Generic use of HEVC SEI messages for multi-layer codecs

ABSTRACT

In an example, a method of coding video data includes coding one or more non-video coding layer (VCL) network abstraction layer (NAL) units of a layer of a multi-layer bitstream, where the one or more non-VCL NAL units contain a decoded picture hash SEI message. The method also includes determining a set of layers of the multi-layer bitstream to which the decoded picture hash SEI message is applicable based on a layer identifier of the one or more non-VCL NAL units containing the decoded picture hash SEI message.

This Application claims the benefit of U.S. Provisional Application61/969,797, filed Mar. 24, 2014, the entire content of which isincorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to video coding and compression, and signalingof data associated with compressed video in a bitstream.

BACKGROUND

Digital video capabilities can be incorporated into a wide range ofdevices, including digital televisions, digital direct broadcastsystems, wireless broadcast systems, personal digital assistants (PDAs),laptop or desktop computers, tablet computers, e-book readers, digitalcameras, digital recording devices, digital media players, video gamingdevices, video game consoles, cellular or satellite radio telephones,so-called “smart phones,” video teleconferencing devices, videostreaming devices, and the like. Digital video devices implement videocompression techniques, such as those described in the standards definedby MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264/MPEG-4, Part 10, AdvancedVideo Coding (AVC), the High Efficiency Video Coding (HEVC) standard,and extensions of such standards. The video devices may transmit,receive, encode, decode, and/or store digital video information moreefficiently by implementing such video compression techniques.

Video compression techniques perform spatial (intra-picture) predictionand/or temporal (inter-picture) prediction to reduce or removeredundancy inherent in video sequences. For block-based video coding, avideo slice (i.e., a video frame or a portion of a video frame) may bepartitioned into video blocks, which may also be referred to astreeblocks, coding units (CUs) and/or coding nodes. Video blocks in aninfra-coded (I) slice of a picture are encoded using spatial predictionwith respect to reference samples in neighboring blocks in the samepicture. Video blocks in an inter-coded (P or B) slice of a picture mayuse spatial prediction with respect to reference samples in neighboringblocks in the same picture or temporal prediction with respect toreference samples in other reference pictures. Pictures may be referredto as frames, and reference pictures may be referred to a referenceframes.

Spatial or temporal prediction results in a predictive block for a blockto be coded. Residual data represents pixel differences between theoriginal block to be coded and the predictive block. An inter-codedblock is encoded according to a motion vector that points to a block ofreference samples forming the predictive block, and the residual dataindicating the difference between the coded block and the predictiveblock. An intra-coded block is encoded according to an intra-coding modeand the residual data. For further compression, the residual data may betransformed from the pixel domain to a transform domain, resulting inresidual transform coefficients, which then may be quantized. Thequantized transform coefficients, initially arranged in atwo-dimensional array, may be scanned in order to produce aone-dimensional vector of transform coefficients, and entropy coding maybe applied to achieve even more compression.

SUMMARY

Aspects of this disclosure are directed to techniques for applyingsupplemental enhancement layer (SEI) messages that are defined in theHigh Efficiency Video Coding (HEVC) standard in a multi-layer context.For example, the techniques of this disclosure may include changes toand/or constraints for a variety of SEI message syntax set forth in HEVCto be applied in multi-layer video coding, e.g., using extensions to theHEVC standard such as a Multi-view Video Coding extension to HEVC(MV-HEVC) or a Scalable Video Coding (SVC) extension to HEVC (SHVC). Insome instances, the techniques may improve computational efficiencyand/or error resilience of such multi-layer codecs.

In an example, a method of coding video data includes obtaining one ormore video coding layer (VCL) network abstraction layer (NAL) units ofan access unit and a first layer of a multi-layer bitstream of videodata, and only coding one or more non-VCL NAL units containing an SEImessage applicable to the VCL NAL units of the first layer together withthe VCL NAL units of the first layer such that within the access unitthe bitstream does not contain any coded pictures of any other layer ofthe multi-layer bitstream between the VCL NAL units of the first layerand the non-VCL NAL units containing the SEI message applicable to theVCL NAL units of the first layer.

In another example, a device for coding video data includes a memoryconfigured to store at least a portion of a multi-layer bitstream ofvideo data, and one or more processors configured to obtain one or morevideo coding layer (VCL) network abstraction layer (NAL) units of anaccess unit and a first layer of the multi-layer bitstream of videodata, and only code one or more non-VCL NAL units containing an SEImessage applicable to the VCL NAL units of the first layer together withthe VCL NAL units of the first layer such that within the access unitthe bitstream does not contain any coded pictures of any other layer ofthe multi-layer bitstream between the VCL NAL units of the first layerand the non-VCL NAL units containing the SEI message applicable to theVCL NAL units of the first layer.

In another example, an apparatus for coding video data includes meansfor obtaining one or more video coding layer (VCL) network abstractionlayer (NAL) units of an access unit and a first layer of a multi-layerbitstream of video data, and means for only coding one or more non-VCLNAL units containing an SEI message applicable to the VCL NAL units ofthe first layer together with the VCL NAL units of the first layer suchthat within the access unit the bitstream does not contain any codedpictures of any other layer of the multi-layer bitstream between the VCLNAL units of the first layer and the non-VCL NAL units containing theSEI message applicable to the VCL NAL units of the first layer.

In another example, a non-transitory computer-readable medium hasinstructions stored thereon that, when executed, cause one or moreprocessors to obtain one or more video coding layer (VCL) networkabstraction layer (NAL) units of an access unit and a first layer of amulti-layer bitstream of video data, and only code one or more non-VCLNAL units containing an SEI message applicable to the VCL NAL units ofthe first layer together with the VCL NAL units of the first layer suchthat within the access unit the bitstream does not contain any codedpictures of any other layer of the multi-layer bitstream between the VCLNAL units of the first layer and the non-VCL NAL units containing theSEI message applicable to the VCL NAL units of the first layer.

In another example, a method of coding video data includes coding one ormore non-video coding layer (VCL) network abstraction layer (NAL) unitsof a layer of a multi-layer bitstream, wherein the one or more non-VCLNAL units contain a decoded picture hash SEI message, and determining aset of layers of the multi-layer bitstream to which the decoded picturehash SEI message is applicable based on a layer identifier of the one ormore non-VCL NAL units containing the decoded picture hash SEI message.

In another example, a device for coding video data includes a memoryconfigured to store at least a portion of a multi-layer bitstream, andone or more processors configured to code one or more non-video codinglayer (VCL) network abstraction layer (NAL) units of a layer of amulti-layer bitstream, wherein the one or more non-VCL NAL units containa decoded picture hash SEI message, and determine a set of layers of themulti-layer bitstream to which the decoded picture hash SEI message isapplicable based on a layer identifier of the one or more non-VCL NALunits containing the decoded picture hash SEI message.

In another example, an apparatus for coding video data includes meansfor coding one or more non-video coding layer (VCL) network abstractionlayer (NAL) units of a layer of a multi-layer bitstream, wherein the oneor more non-VCL NAL units contain a decoded picture hash SEI message,and means for determining a set of layers of the multi-layer bitstreamto which the decoded picture hash SEI message is applicable based on alayer identifier of the one or more non-VCL NAL units containing thedecoded picture hash SEI message.

In another example, a non-transitory computer-readable medium hasinstructions stored thereon that, when executed, cause one or moreprocessors to code one or more non-video coding layer (VCL) networkabstraction layer (NAL) units of a layer of a multi-layer bitstream,wherein the one or more non-VCL NAL units contain a decoded picture hashSEI message, and determine a set of layers of the multi-layer bitstreamto which the decoded picture hash SEI message is applicable based on alayer identifier of the one or more non-VCL NAL units containing thedecoded picture hash SEI message.

In another example, a method of coding video data includes coding one ormore non-video coding layer (VCL) network abstraction layer (NAL) unitsof a layer of a multi-layer bitstream of video data, wherein the one ormore non-VCL NAL units contain an SEI message having an SEI payloadtype, and determining one or more syntax values of the multi-layerbitstream to which the SEI message applies based on the SEI payloadtype.

In another example, a device for coding video data includes a memoryconfigured to store a layer of a multi-layer bitstream, and one or moreprocessors configured to code one or more non-video coding layer (VCL)network abstraction layer (NAL) units of a layer of a multi-layerbitstream of video data, wherein the one or more non-VCL NAL unitscontain an SEI message having an SEI payload type, and determine one ormore syntax values of the multi-layer bitstream to which the SEI messageapplies based on the SEI payload type.

In another example, an apparatus for coding video data includes meansfor coding one or more non-video coding layer (VCL) network abstractionlayer (NAL) units of a layer of a multi-layer bitstream of video data,wherein the one or more non-VCL NAL units contain an SEI message havingan SEI payload type, and means for determining one or more syntax valuesof the multi-layer bitstream to which the SEI message applies based onthe SEI payload type.

In another example, a non-transitory computer-readable medium hasinstructions stored thereon that, when executed, cause one or moreprocessors to code one or more non-video coding layer (VCL) networkabstraction layer (NAL) units of a layer of a multi-layer bitstream ofvideo data, wherein the one or more non-VCL NAL units contain an SEImessage having an SEI payload type, and determine one or more syntaxvalues of the multi-layer bitstream to which the SEI message appliesbased on the SEI payload type.

The details of one or more examples of the disclosure are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages will be apparent from the description, drawings,and claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example video encoding anddecoding system that may utilize the techniques described in thisdisclosure.

FIG. 2 is a block diagram illustrating an example video encoder that mayimplement the techniques described in this disclosure.

FIG. 3 is a block diagram illustrating an example video decoder that mayimplement the techniques described in this disclosure.

FIG. 4 is a block diagram illustrating one example of an encapsulationunit in which one or more aspects of this disclosure could beimplemented.

FIG. 5 is a block diagram illustrating one example network in which oneor more aspects of this disclosure could be implemented.

FIG. 6 is a flow diagram illustrating an example operation of a videoprocessing device configured to code an SEI message in accordance withvarious aspects of the techniques described in this disclosure.

FIG. 7 is a flow diagram illustrating another example operation of avideo processing device configured to code an SEI message in accordancewith various aspects of the techniques described in this disclosure.

FIG. 8 is a flow diagram illustrating another example operation of avideo processing device configured to code an SEI message in accordancewith various aspects of the techniques described in this disclosure.

DETAILED DESCRIPTION

This disclosure includes techniques for applying supplementalenhancement layer (SEI) messages that are defined in the High EfficiencyVideo Coding (HEVC) standard in a multi-layer context. In someinstances, the techniques may be performed with multi-layer extensionsto the HEVC standard such as a Multi-view Video Coding extension to HEVC(MV-HEVC) or a Scalable Video Coding (SVC) extension to HEVC (SHVC), asnoted below. The techniques of this disclosure, however, are not limitedto any particular video coding standard, and may also or alternativelybe used with other extensions to HEVC, other multi-view coding standardsand/or other multi-layer video standards. In addition, techniques ofthis disclosure, as described below, may be applied independently or incombination.

A “layer” of video data may generally refer to a sequence of pictureshaving at least one common characteristic, such as a view, a frame rate,a resolution, or the like. For example, a layer may include video dataassociated with a particular view (e.g., perspective) of multi-viewvideo data. As another example, a layer may include video dataassociated with a particular layer of scalable video data. Thus, thisdisclosure may interchangeably refer to a layer and a view of videodata. That is, a view of video data may be referred to as a layer ofvideo data, and vice versa, and a plurality of views or a plurality ofscalable layers may be referred to, in a similar manner, as multiplelayers, e.g., in a multi-layer coding system, m addition, a multi-layercodec (also referred to as a multi-layer video coder or multi-layerencoder-decoder) may refer to a multi-view codec or a scalable codec(e.g., a codec configured to encode and/or decode video data usingMV-HEVC, SHVC, or another multi-layer coding technique).

A multi-layer bitstream may include a base layer and one or morenon-base layers, e.g., in SHVC, or a plurality of views, e.g., inMV-HEVC. In a scalable bitstream, the base layer may typically have alayer identifier that is equal to zero. A non-base layer may have alayer identifier that is greater than zero, and may provide additionalvideo data that is not included in the base layer. For example, anon-base layer of multi-view video data may include an additional viewof video data. A non-base layer of scalable video data may include anadditional layer of scalable video data. A non-base layer may beinterchangeably referred to as an enhancement layer.

An access unit (sometimes abbreviated as AU) of a multi-layer bitstreamis, generally, a unit of data including all layer components (e.g., allnetwork abstraction layer (NAL) units) for a common temporal instance.The layer components of an access unit are typically intended to beoutput together (i.e., output substantially simultaneously), whereoutputting a picture generally involves transferring pictures from adecoded picture buffer (DPB) (e.g., storing pictures from the DPB to anexternal memory, sending the pictures from the DPB to a display, or thelike).

A bitstream containing an encoded representation of video data mayinclude a series of network abstraction layer (NAL) units. A NAL unitmay be a syntax structure containing an indication of the type of datain the NAL unit and bytes containing that data in the form of a raw bytesequence payload (RBSP) interspersed as necessary with emulationprevention bits. The NAL units may include video coding layer (VCL) NALunits and non-VCL NAL units. The VCL NAL units may include coded slicesof pictures. A non-VCL NAL unit may encapsulate a video parameter set(VPS), a sequence parameter set (SPS), a picture parameter set (PPS),one or more supplemental enhancement information (SEI) messages, orother types of data.

NAL units of the bitstream may be associated with different layers ofthe bitstream. In SHVC, as noted above, the layers other than a baselayer may be referred to as “enhancement layers” and may include datathat improve the quality of playback of the video data. In multi-viewcoding and 3-dimensional video (3DV) coding, such as MV-HEVC, the layersmay include data associated with different views. Each layer of thebitstream is associated with a different layer identifier.

In addition, NAL units may include temporal identifiers. Each operationpoint of a bitstream has a set of layer identifiers and a temporalidentifier. If a NAL unit specifies a layer identifier in the set oflayer identifiers for an operation point and the temporal identifier ofthe NAL unit is less than or equal to the temporal identifier of theoperation point, the NAL unit is associated with the operation point.

The SEI mechanism supported in both H.264/AVC and HEVC enables videoencoders to include such metadata in the bitstream that is not requiredfor correct decoding, by a video decoder or other device, of the samplevalues of the output pictures, but can be used for various otherpurposes, such as picture output timing, displaying, as well as lossdetection and concealment. A NAL unit that encapsulates one or more SEImessages is referred to herein as a SEI NAL unit. One type of SEImessage is a scalable nesting SEI message. A scalable nesting SEImessage is an SEI message that contains one or more additional SEImessages. The scalable nesting SEI message may be used to indicatewhether an SEI message applies to particular layers or temporalsub-layers of a multi-layer bitstream. An SEI message that is notcontained in a scalable nesting SEI message is referred to herein as anon-nested SEI message.

Certain types of SEI messages contain information that is onlyapplicable to particular operation points. An operation point of abitstream is associated with a set of layer identifiers and a temporalidentifier. An operation point representation may include each NAL unitthat is associated with an operation point. An operation pointrepresentation may have a different frame rate and/or bit rate than anoriginal bitstream. This is because the operation point representationmay not include some pictures and/or some of the data of the originalbitstream.

Buffering period SEI messages, picture timing SEI messages, and decodingunit SEI messages may only be applicable to particular operation points.Thus, in order to use the information in such SEI messages, a videoprocessor may determine which operation points are applicable to the SEImessages. Other types of SEI messages are only applicable to particularlayers. Thus, in order to use the information in such SEI messages, thevideo processor may determine which layers are applicable to the SEImessages.

Generic use of HEVC SEI messages in the context of multi-layer codingmay present several challenges. For example, as described in greaterdetail below, applying the SEI messages specified in HEVC to multiplelayers may increase complexity, create syntax inconsistencies, and/orcreate other errors that cause a multi-layer video codec to malfunction.

In some examples, the techniques of this disclosure may providesolutions to resolve a variety of issues related to generic use of HEVCSEI messages. For example, the techniques may include applyingconstraints on certain syntax elements, such that a video encoder orvideo decoder automatically codes (or automatically determines, withoutcoding) values for the certain syntax elements based on characteristicsof a multi-layer bitstream.

FIG. 1 is a block diagram illustrating an example video encoding anddecoding system 10 that may utilize the techniques described in thisdisclosure. As shown in FIG. 1, system 10 includes a source device 12that generates encoded video data to be decoded at a later time by adestination device 14. Source device 12 and destination device 14 maycomprise any of a wide range of devices, including desktop computers,notebook (i.e., laptop) computers, tablet computers, set-top boxes,telephone handsets such as so-called “smart” phones, so-called “smart”pads, televisions, cameras, display-devices, digital media players,video gaming consoles, video streaming device, or the like. In somecases, source device 12 and destination device 14 may be equipped forwireless communication.

Destination device 14 may receive the encoded video data to be decodedvia a fink 16. Link 16 may comprise any type of medium or device capableof moving the encoded video data from source device 12 to destinationdevice 14. In one example, link 16 may comprise a communication mediumto enable source device 12 to transmit encoded video data directly todestination device 14 in real-time. The encoded video data may bemodulated according to a communication standard, such as a wirelesscommunication protocol, and transmitted to destination device 14. Thecommunication medium may comprise any wireless or wired communicationmedium, such as a radio frequency (RF) spectrum or one or more physicaltransmission lines. The communication medium may form part of apacket-based network, such as a local area network, a wide-area network,or a global network such as the Internet. The communication medium mayinclude routers, switches, base stations, or any other equipment thatmay be useful to facilitate communication from source device 12 todestination device 14.

Alternatively, encoded data may be output from output interface 22 to astorage device 32. Similarly, encoded data may be accessed from storagedevice 32 by input, interface. Storage device 32 may include any of avariety of distributed or locally accessed data storage media such as ahard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile ornon-volatile memory, or any other suitable digital storage media forstoring encoded video data. In a further example, storage device 32 maycorrespond to a file server or another intermediate storage device thatmay hold the encoded video generated by source device 12. Destinationdevice 14 may access stored video data from storage device 32 viastreaming or download. The file server may be any type of server capableof storing encoded video data and transmitting that encoded video datato the destination device 14. Example fife servers include a web server(e.g., for a website), an FTP server, network attached storage (NAS)devices, or a local disk drive. Destination device 14 may access theencoded video data through any standard data connection, including anInternet connection. This may include a wireless channel (e.g., a Wi-Ficonnection), a wired connection (e.g., DSL, cable modem, etc.), or acombination of both that is suitable for accessing encoded video datastored on a file server. The transmission of encoded video data fromstorage device 32 may be a streaming transmission, a downloadtransmission, or a combination of both.

The techniques of this disclosure are not necessarily limited towireless applications or settings. The techniques may be applied tovideo coding in support of any of a variety of multimedia applications,such as over-the-air television broadcasts, cable televisiontransmissions, satellite television transmissions, streaming videotransmissions, e.g., via the Internet, encoding of digital video forstorage on a data storage medium, decoding of digital video stored on adata storage medium, or other applications. In some examples, system 10may be configured to support one-way or two-way video transmission tosupport applications such as video streaming, video playback, videobroadcasting, and/or video telephony.

In the example of FIG. 1, source device 12 includes a video source 18,video encoder 20, encapsulation unit 21, and an output interface 22. Insome cases, output interface 22 may include a modulator/demodulator(modem) and/or a transmitter. In source device 12, video source 18 mayinclude a source such as a video capture device, e.g., a video camera, avideo archive containing previously captured video, a video feedinterface to receive video from a video content provider, and/or acomputer graphics system for generating computer graphics data as thesource video, or a combination of such sources. As one example, if videosource 18 is a video camera, source device 12 and destination device 14may form so-called camera phones or video phones. However, thetechniques described in this disclosure may be applicable to videocoding in general, and may be applied to wireless and/or wiredapplications.

The captured, pre-captured, or computer-generated video may be encodedby-video encoder 20. Encapsulation unit 21 may form one or morerepresentations of the multimedia content, where each of therepresentations may include one or more layers. In some examples, videoencoder 20 may encode each layer in different ways, e.g., with differentframe rates, different bit rates, different resolutions, or other suchdifferences. Thus, encapsulation unit 21 may form variousrepresentations having various characteristics, e.g., bit rate, framerate, resolution, and the like.

Each of the representations may correspond to respective bitstreams thatcan be retrieved by destination device 14. Encapsulation unit 21 mayprovide an indication of a range of view identifiers (view_ids) forviews included in each representation, e.g., within a media presentationdescription (MPD) data structure for the multimedia content. Forexample, encapsulation unit 21 may provide an indication of a maximumview identifier and a minimum view identifier for the views of arepresentation. The MPD may further provide indications of maximumnumbers of views targeted for output for each of a plurality ofrepresentations of the multimedia content. The MPD or data thereof may,in some examples, be stored in a manifest for the representation(s).

The encoded video data may be transmitted directly to destination device14 via output interface 22 of source device 12. The encoded video datamay also (or alternatively) be stored onto storage device 32 for lateraccess by destination device 14 or other devices, for decoding and/orplayback.

Destination device 14 includes an input interface 28, decapsulation unit29, a video decoder 30, and a display device 31. In some cases, inputinterface 28 may include a receiver and/or a modem. Input interface 28of destination device 14 receives the encoded video data over link 16.The encoded video data communicated over link 16, or provided on storagedevice 32, may include a variety of syntax elements generated by videoencoder 20 for use by a video decoder, such as video decoder 30, indecoding the video data. Such syntax elements may be included with theencoded video data transmitted on a communication medium, stored on astorage medium, or stored on a file server.

Decapsulation unit 29 of destination device 14 may represent a unit thatdecapsulates SEI messages from a bitstream (or a subset of a bitstream,referred to as an operation point in the context of multi-layer coding).Decapsulation unit 29 may perform operations in an order opposite tothose performed by encapsulation unit 21 to decapsulate data from theencapsulated encoded bitstream, such as SEI messages.

Display device 31 may be integrated with, or external to, destinationdevice 14. In some examples, destination device 14 may include anintegrated display device and also be configured to interface with anexternal display device. In other examples, destination device 14 may bea display device. In general, display device 31 displays the decodedvideo data to a user, and may comprise any of a variety of displaydevices such as a liquid crystal display (LCD), a plasma display, anorganic light emitting diode (OLED) display, or another type of displaydevice.

Video encoder 20 and video decoder 30 each may be implemented as any ofa variety of suitable encoder circuitry, such as one or moremicroprocessors, digital signal processors (DSPs), application specificintegrated circuits (ASICs), field programmable gate arrays (FPGAs),discrete logic, software, hardware, firmware or any combinationsthereof. When the techniques are implemented partially in software, adevice may store instructions for the software in a suitable,non-transitory computer-readable medium and execute the instructions inhardware using one or more processors to perform the techniques of thisdisclosure. Each of video encoder 20 and video decoder 30 may beincluded in one or more encoders or decoders, either of which may beintegrated as part of a combined encoder/decoder (CODEC) in a respectivedevice.

Although not shown in FIG. 1, in some aspects, video encoder 20 andvideo decoder 30 may each be integrated with an audio encoder anddecoder, and may include appropriate MUX-DEMUX units, or other hardwareand software, to handle encoding of both audio and video in a commondata stream or separate data streams. If applicable, in some examples,MUX-DEMUX units may conform to the ITU H.223 multiplexer protocol, orother protocols such as the user datagram protocol (UDP).

This disclosure may generally refer to video encoder 20 “signaling”certain information to another device, such as video decoder 30. Theterm “signaling” may generally refer to the communication of syntaxelements and/or other data used to decode the compressed video data.Such communication may occur in real- or near-real-time. Alternately,such communication may occur over a span of time, such as might occurwhen storing syntax elements to a computer-readable storage medium in anencoded bitstream at the time of encoding, which then may be retrievedby a decoding device at any time after being stored to this medium.

In some examples, video encoder 20 and video decoder 30 operateaccording to a video compression standard, such as ISO/IEC MPEG-4 Visualand ITU-T H.264 (also known as ISO/IEC MPEG-4 AVC), including itsScalable Video Coding (SVC) extension, Muitiview Video Coding (MVC)extension, and MVC-based 3DV extension. In other examples, video encoder20 and video decoder 30 may operate according to the High EfficiencyVideo Coding (HEVC) developed by the Joint Collaboration Team on VideoCoding (JCT-VC) of ITU-T Video Coding Experts Group (VCEG) and ISO/IECMotion Picture Experts Group (MPEG). A draft of the HEVC standard isdescribed in ITU-T H.265, High Efficiency Video Coding, April, 2014 andWang et al, “High Efficiency Video Coding (HEVC) defect report 3,” JointCollaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 andISO/IEC JTC1/SC29/WG11, document JCTVC-P1003_v1, 16^(th) Meeting, SanJose, January 2014 Wang et al., “High Efficiency Video Coding (HEVC)defect report 3,” Joint Collaborative Team on Video Coding (JCT-VC) ofITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, document JCTVC-P1003_v1,16^(th) Meeting, San Jose, January 2014, which provides a third defectreport for HEVC Version 1.

Furthermore, there are ongoing efforts to produce scalable video coding,multi-view coding, and 3DV extensions for HEVC. The scalable videocoding extension of HEVC may be referred to as SHEVC. A recent WorkingDraft (WD) of SHVC (referred to as SHVC WD5 or the current SHVC WDhereinafter), is described in Chen et al, “High Efficiency Video Coding(HEVC) scalable extension draft 5,” Joint Collaborative Team on VideoCoding (JCT-VC) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, documentJCTVC-P1008_v4, 16^(th) Meeting, San Jose, January 2014. A recentWorking Draft (WD) of MV-HEVC (referred to as MV-HEVC WD7 or the currentMV-HEVC WD hereinafter) is described in Tech et al., “MV-HEVC Draft Text7,” Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3and ISO/IEC JTC1/SC29/WG11, document JCTVC-G1004_v7, 16^(th) Meeting,San Jose, January 2014.

In HEVC and other video coding specifications, a video sequencetypically includes a series of pictures. Pictures may also be referredto as “frames.” A picture may include three sample arrays, denotedS_(L), S_(Cb), and S_(Cr). S_(L) is a two-dimensional array (i.e., ablock) of luma samples. S_(Cb), is a two-dimensional array of Cbchrominance samples. S_(Cr) is a two-dimensional array of Cr chrominancesamples. Chrominance samples may also be referred to herein as “chroma”samples. In other instances, a picture may be monochrome and may onlyinclude an array of luma samples.

To generate an encoded representation of a picture, video encoder 20 maygenerate a set of coding tree units (CTUs). Each of the CTUs maycomprise a coding tree block of luma samples, two corresponding codingtree blocks of chroma samples, and syntax structures used to code thesamples of the coding tree blocks. In monochrome pictures or pictureshaving three separate color planes, a CTU may comprise a single codingtree block and syntax structures used to code the samples of the codingfree block. A coding tree block may be an N×N block of samples. A CTUmay also be referred to as a “tree block” or a “largest coding unit”(LCU). The CTUs of HEVC may be broadly analogous to the macroblocks ofother standards, such as H.264/AVC. However, a CTU is not necessarilylimited to a particular size and may include one or more coding units(CUs). A slice may include an integer number of CTUs orderedconsecutively in a raster scan order.

To generate a coded CTU, video encoder 20 may recursively performquad-tree partitioning on the coding tree blocks of a CTU to divide thecoding tree blocks into coding blocks, hence the name “coding treeunits.” A coding block may be an N×N block of samples. A CU may comprisea coding block of luma samples and two corresponding coding blocks ofchroma samples of a picture that has a luma sample array, a Cb samplearray, and a Cr sample array, and syntax structures used to code thesamples of the coding blocks. In monochrome pictures or pictures havingthree separate color planes, a CU may comprise a single coding block andsyntax structures used to code the samples of the coding block.

Video encoder 20 may partition a coding block of a CU into one or moreprediction blocks. A prediction block is a rectangular (i.e., square ornon-square) block of samples on which the same prediction is applied. Aprediction unit (PU) of a CU may comprise a prediction block of lumasamples, two corresponding prediction blocks of chroma samples, andsyntax structures used to predict the prediction blocks. In monochromepictures or pictures having three separate color planes, a PU maycomprise a single prediction block and syntax structures used to predictthe prediction block. Video encoder 20 may generate predictive luma, Cb,and Cr blocks for luma, Cb, and Cr prediction blocks of each PU of theCU.

Video encoder 20 may use infra-prediction or inter prediction togenerate the predictive blocks for a PU. If video encoder 20 usesintra-prediction to generate the predictive blocks of a PU, videoencoder 20 may generate the predictive blocks of the PU based on decodedsamples of the picture associated with the PU. If video encoder 20 usesinter prediction to generate the predictive blocks of a PU, videoencoder 20 may generate the predictive blocks of the PU based on decodedsamples of one or more pictures other than the picture associated withthe PU.

After video encoder 20 generates predictive lunia, Cb, and Cr blocks forone or more PUs of a CU, video encoder 20 may generate a luma residualblock for the CU. Each sample in the CU's luma residual block indicatesa difference between a luma sample in one of the CU's predictive lumablocks and a corresponding sample in the CU's original luma codingblock. In addition, video encoder 20 may generate a Cb residual blockfor the CU. Each sample in the CU's Cb residual block may indicate adifference between a Cb sample in one of the CU's predictive Cb blocksand a corresponding sample in the CU's original Cb coding block. Videoencoder 20 may also generate a Cr residual block for the CU. Each samplein the CU's Cr residual block may indicate a difference between a Crsample in one of the CU's predictive Cr blocks and a correspondingsample in the CU's original Cr coding block.

Furthermore, video encoder 20 may use quad-free partitioning todecompose the luma, Cb, and Cr residual blocks of a CU into one or moreluma, Cb, and Cr transform blocks. A transform block is a rectangular(e.g., square or non-square) block of samples on which the sametransform is applied. A transform unit (TU) of a CU may comprise atransform block of luma samples, two corresponding transform blocks ofchroma samples, and syntax structures used to transform the transformblock samples. Thus, each TU of a CU may be associated with a lumatransform block, a Cb transform block, and a Cr transform block. Theluma transform block associated with the TU may be a sub-block of theCU's luma residual block. The Cb transform block may be a sub-block ofthe CU's Cb residual block. The Cr transform block may be a sub-block ofthe CU's Cr residual block. In monochrome pictures or pictures havingthree separate color planes, a TU may comprise a single transform blockand syntax structures used to transform the samples of the transformblock.

Video encoder 20 may apply one or more transforms to a luma transformblock of a TU to generate a luma coefficient block for the TU. Acoefficient block may be a two-dimensional array of transformcoefficients. A transform coefficient may be a scalar quantity. Videoencoder 20 may apply one or more transforms to a Cb transform block of aTU to generate a Cb coefficient block for the TU. Video encoder 20 mayapply one or more transforms to a Cr transform block of a TU to generatea Cr coefficient block for the TU.

After generating a coefficient block (e.g., a luma coefficient block, aCb coefficient block or a Cr coefficient block), video encoder 20 mayquantize the coefficient block. Quantization generally refers to aprocess in which transform coefficients are quantized to possibly reducethe amount of data used to represent the transform coefficients,providing further compression. After video encoder 20 quantizes acoefficient block, video encoder 20 may entropy encode syntax elementsindicating the quantized transform coefficients. For example, videoencoder 20 may perform Context-Adaptive Binary Arithmetic Coding (CABAC)on the syntax elements indicating the quantized transform coefficients.

Video encoder 20 may output a bitstream that includes a sequence of bitsthat forms a representation of coded pictures and associated data. Thebitstream may comprise a sequence of network abstraction layer (NAL)units. A NAL unit is a syntax structure containing an indication of thetype of data in the NAL unit and bytes containing that data in the formof a raw byte sequence pay load (RBSP) interspersed as necessary withemulation prevention bits. Each of the NAL units includes a NAL unitheader and encapsulates a RBSP. The NAL unit header may include a syntaxelement that indicates a NAL unit type code. The NAL unit type codespecified by the NAL unit header of a NAL unit indicates the type of theNAL unit. A RBSP may be a syntax structure containing an integer numberof bytes that is encapsulated within a NAL unit. In some instances, anRBSP includes zero bits.

Different types of NAL units may encapsulate different types of RBSPs.For example, a first type of NAL unit may encapsulate an RBSP for apicture parameter set (PPS), a second type of NAL unit may encapsulatean RBSP for a coded slice, a third type of NAL unit may encapsulate anRBSP for SEI, and so on. NAL units that encapsulate RBSPs for videocoding data (as opposed to RBSPs for parameter sets and SEI messages)may be referred to as video coding layer (VCL) NAL units.

Video decoder 30 may receive a bitstream generated by video encoder 20.In addition, video decoder 30 may parse the bitstream to obtain syntaxelements from the bitstream. Video decoder 30 may reconstruct thepictures of the video data based at least in part on the syntax elementsobtained from the bitstream. The process to reconstruct the video datamay be generally reciprocal to the process performed by video encoder20. In addition, video decoder 30 may inverse quantize coefficientblocks associated with TUs of a current CU. Video decoder 30 may performinverse transforms on the coefficient blocks to reconstruct transformblocks associated with the TUs of the current CU. Video decoder 30 mayreconstruct the coding blocks of the current CU by adding the samples ofthe predictive blocks for PUs of the current CU to corresponding samplesof the transform blocks of the TUs of the current CU. By reconstructingthe coding blocks for each CU of a picture, video decoder 30 mayreconstruct the picture.

In multi-view coding, there may be multiple views of the same scene fromdifferent viewpoints. As noted above, an access unit includes a set ofpictures that correspond to the same time instance. Thus, video data maybe conceptualized as a series of access units occurring over time. A“view component” may be a coded representation of a view in a singleaccess unit. In this disclosure, a “view” may refer to a sequence ofview components associated with the same view identifier. Example typesof view components include texture view components and depth viewcomponents.

Multi-view coding supports inter-view prediction. Inter-view predictionis similar to the inter prediction used in HEVC and may use the samesyntax elements. However, when a video coder performs inter-viewprediction on a current video unit (such as a PU), video encoder 20 mayuse, as a reference picture, a picture that is in the same access unitas the current video unit, but in a different view. In contrast,conventional inter prediction only uses pictures in different accessunits as reference pictures.

In multi-view coding, a view may be referred to as a “base view” if avideo decoder (e.g., video decoder 30) can decode pictures in the viewwithout reference to pictures in any other view. When coding a picturein one of the non-base views, a video coder (such as video encoder 20 orvideo decoder 30) may add a picture into a reference picture list if thepicture is in a different view but within a same time instance (i.e.,access unit) as the picture that the video coder is currently coding.Like other inter prediction reference pictures, the video coder mayinsert an inter-view prediction reference picture at any position of areference picture list.

The SEI mechanism supported in both H.264/AVC and HEVC enables videoencoders (e.g., video encoder 20) to include such metadata in thebitstream that is not required for correct decoding of the sample valuesof the output pictures, but can be used for various other purposes, suchas picture output timing, displaying, as well as loss detection andconcealment. Video encoder 20 may use SEI messages to include, in thebitstream, metadata that is not required for correct decoding of thesample values of pictures. However, video decoder 30 or other devicesmay use the metadata included in SEI messages for various otherpurposes. For example, video decoder 30 or another device may use themetadata in SEI messages for picture output timing, picture displaying,loss detection, and error concealment.

Video encoder 20 may include one or more SEI NAL units in an accessunit. In other words, any number of SEI NAL units may be associated withan access unit. Furthermore, each SEI NAL unit, may contain one or moreSEI messages. That is, video encoders can include any number of SEI NALunits in an access unit, and each SEI NAL unit may contain one or moreSEI messages. A SEI NAL unit may include a NAL unit header and apayload. The NAL unit header of the SEI NAL unit includes at least afirst syntax element and a second syntax element. The first syntaxelement specifies a layer identifier of the SEI NAL unit. The secondsyntax element specifies a temporal identifier of the SEI NAL unit.

A nested SEI message refers to an SEI message that is contained in ascalable nesting SEI message. A non-nested SEI message refers to an SEImessage that is not contained in a scalable nesting SEI message. Thepayload of the SEI NAL unit may comprise a nested SEI message or anon-nested SEI message.

The HEVC standard describes the syntax and semantics for various typesof SEI messages. However, the HEVC standard does not describe thehandling of the SEI messages because the SEI messages do not affect thenormative decoding process. One reason to have SEI messages in the HEVCstandard is to enable supplemental data being interpreted identically indifferent systems using HEVC. Specifications and systems using HEVC mayrequire video encoders to generate certain SEI messages or may definespecific handling of particular types of received SEI messages.

Table 1, below, lists SEI messages specified in HEVC and brieflydescribes their purposes:

TABLE 1 Overview of SEI messages SEI message Purpose Buffering periodInitial delays for hypothetical reference decoder (HRD) operationPicture timing Picture output time and picture/sub-picture removal timefor HRD operation, as well as picture structure related informationPan-scan rectangle Displaying at a different picture aspect ratio (PAR)than the PAR of the output pictures Filler payload Adjusting the bitrateto meet specific constraints User data registered SEI messages to bespecified by external entities User data unregistered Recovery pointAdditional information for clean random access. Gradual decodingrefresh. Scene information Information about scene changes andtransitions Full-frame snapshot Indication to label the associateddecoded picture as a still-image snapshot of the video contentProgressive Indicates that certain consecutive pictures represent arefinement segment progressive refinement of the quality of a picturerather than a moving scene Film grain Enables decoders to synthesizefilm grain characteristics Deblocking filter Recommends whether or notdisplayed pictures should undergo display preference the in-loopdeblocking filter process Post-filter hint Provides suggestedpost-filter coefficients or correlation information for post-filterdesign Tone mapping Remapping to another color space than that used orassumed in information encoding Frame packing Packing of stereoscopicvideo into an HEVC bitstream arrangement Display orientation Specifiesflipping and/or rotation that should be applied to the output pictureswhen they are displayed Structure of pictures Describes the temporal andinter prediction structure of the description bitstream Decoded picturehash Checksum of the decoded picture, which may be used for errordetection Active parameter sets Provides information on of active VPS,SPS, etc. Decoding unit Sub-picture removal time for HRD operation, aswell as information decoding unit index Temporal level zero Providestemporal level zero index values index Scalable nesting Provides amechanism to nest SEI messages for association to different operationpoints and layers Region refresh Provides information on refreshed andnon-refreshed region for information gradual decoding refresh

One potential issue with using HEVC SEI messages in a multi-layercontext is that an SEI NAL unit containing an SEI message that appliesto a layer with a layer identifier (e.g., as identified by anuh_layer_id syntax element of the bitstream) that is equal to a firstlayer (layerIdA for purposes of example) is permitted to follow a VCLNAL unit of a picture with a layer identifier (nuh_layer_id) that isgreater than the first layer (layerIdA) within an access unit (AU) thatcontains pictures of the layers. For example, an SEI message may beseparated in the bitstream from the picture using the SEI message.

In an example for purposes of illustration, an access unit may include afirst picture of a first layer of a multi-layer bitstream and a secondpicture of a second layer of a multi-layer bitstream. In some instances,an SEI message that is applicable to the first picture of the firstlayer may be included with the NAL units associated with the secondlayer. If an SEI NAL unit is permitted to be included with other layersof video data, video encoder 20 and/or video decoder 30 may have toextract the SEI NAL unit from the other layers and store the messageprior to coding the access unit.

According to a first aspect of this disclosure, an SEI NAL unitcontaining an SEI message that applies to a layer with a layeridentifier (nuh_layer_id) that is equal to a first layer (layerIdA) isdisallowed to follow any VCL NAL unit as well as its associated non-VCLNAL units of a picture with a layer identifier (nuh_layer_id) that isgreater than the first layer (layerIdA) within the access unit. Forexample, according to aspects of this disclosure, placement of SEI NALunits may be constrained such that an SEI NAL unit is together with thelayer (or layers) to which the SEI NAL unit applies in the multi-layerbitstream.

In the example above, video encoder 20 and/or video decoder 30 may onlycode one or more non-VCL NAL units containing an SEI message applicableto VCL NAL units of a first layer together with the VCL NAL units of thefirst layer (e.g., successively code the SEI NAL unit and VCL NALunits), such that the bitstream does not contain any coded pictures ofany other layer of the multi-layer bitstream between the VCL NAL unitsof the first layer and the non-VCL NAL units containing the SEI messageapplicable to the VCL NAL units of the first layer. In some instances,having the SEI NAL unit together in a multi-layer bitstream with thepictures in the layers to which the SEI NAL unit applies may bebeneficial, e.g., in minimizing storage or transmission overhead whenstoring and transmitting associated NAL units together. For example, bykeeping the non-VCL and VCL NAL units to which the non-VCL NAL unitsapply together in the bitstream, video encoder 20 and/or video decoder30 may not have to locate and fetch the non-VCL NAL units from memoryprior to coding the VCL NAL units.

A second potential issue with using HEVC SEI messages in a multi-layercontext is that a set of applicable layers of a multi-layer bitstream towhich a decoded picture hash SEI message is not clearly specified in theHEVC standard. The decoded picture hash SEI message provides a checksumderived from the sample values of a decoded picture. The decoded picturehash message may be used for detecting whether a picture was correctlyreceived and decoded.

According to a second aspect of this disclosure, the set of applicablelayers of a decoded picture hash SEI message may be specified to be thelayer with the layer identifier (nuh_layer_id) that is equal to thelayer identifier (nuh_layer_id) of the SEI NAL unit containing the SEImessage and the decoded picture hash SEI message is not permitted to benested. For example, according to aspects of this disclosure, videoencoder 20 and/or video decoder 30 may only code one decoded picturehash SEI message in an SEI NAL unit as a non-nested SEI message and thedecoded picture hash SEI message only applies to the layer that has thesame layer identifier (nuh_layer_id) of the SEI NAL unit that containsthe SEI message.

In the example above, video encoder 20 and/or video decoder 30 may codeone or more non-VCL NAL units (e.g., SEI NAL units) containing a decodedpicture hash SEI message, and determine a set of layers of themulti-layer bitstream to which the decoded picture hash SEI message isapplicable based on a layer identifier of the one or more non-VCL NALunits containing the decoded picture hash SEI message. Video encoder 20and/or video decoder 30 may code one or more syntax elements thatindicate the layer identifier for the SEI NAL unit, such as anuh_layer_id syntax element, such that determining the set of layers isbased on the syntax element. The techniques may, in some instances,increase error resilience and/or reduce storage overhead associated withdecoded picture hash SEI messages in multi-layer coding.

A third potential issue with using HEVC SEI messages in a multi-layercontext is that the set of applicable layers of an active parameter setsSEI message is not clearly specified in the HEVC standard. The activeparameter sets SEI message indicates which VPS is active for the VCL NALunits of the access unit associated with the SEI message. The SEImessage may also provide information on which SPS is active for the VCLNAL units of the access unit associated with the SEI message, and otherinformation related to parameter sets. For example, the SEI message mayinclude an indication of whether full random accessibility is supported(e.g., when supported, all parameter sets needed for decoding of theremaining pictures of the bitstream when random accessing from thebeginning of the current coded video sequence by completely discardingall access units earlier in decoding order are present in the remainingbitstream and all coded pictures in the remaining bitstream can becorrectly decoded), or whether there is no parameter set within thecurrent coded video sequence that updates another parameter set of thesame type preceding in decoding order (e.g., an update of a parameterset refers to the use of the same parameter set identifier, but withsome other parameters changed).

According to a third aspect of this disclosure, an active parameter setsSEI message is defined to apply to all layers in the bitstream. Inaddition, the active parameter sets SEI message is constrained frombeing nested. In this example, video encoder 20 and/or video decoder 30may code one or more non-VCL NAL units of a multi-layer bitstream thatcontain an active parameter sets SEI message, and determine that theactive parameter sets SEI message is applicable to all layers of themulti-layer bitstream based on the one or more non-VCL NAL unitscontaining the active parameter set SEI message. For example, videoencoder 20 and/or video decoder 30 may automatically derive that theactive parameter sets SEI message applies to all layers of themulti-layer bitstream by virtue of coding the active parameter sets SEImessage. In some instances, the techniques may reduce the complexityassociated with active parameter sets SEI messages in multi-layercoding.

A fourth potential issue with using HEVC SEI messages in a multi-layercontext is that when a frame_field_info_present_flag syntax element isequal to one for a picture timing information SEI message, nested ornon-nested, the set of applicable layers is not clearly specified forthe frame-field information carried in the syntax elements pic_struct,source_scan_type, and duplicate_flag. For example, aframe_field_info_present_flag syntax element that is equal to onespecifies that picture timing SEI messages are present for every pictureand include the pic_struct, source_scan_type, and duplicate_flag syntaxelements. In general, the pic_struct syntax element indicates whether apicture should be displayed as a frame or as one or more fields, thesource_scan_type syntax element indicates a scan type (e.g.,progressive, interfaced, or unknown), and the duplicate_flag syntaxelement indicates that the current picture is indicated to be aduplicate of a previous picture in output order.

According to a fourth aspect of this disclosure, when theframe_field_info_present_flag syntax element is equal to one for apicture timing information SEI message, nested or non-nested, videoencoder 20 and/or video decoder 30 may automatically determine that theframe-field information carried in the syntax elements pic_struct,source_scan_type, and duplicate_flag applies to the layers in all of theoperation points to which the picture timing SEI message applies. Inthis manner, in some instances, the techniques may reduce the complexityand/or improve error resilience when using theframe_field_info_present_flag syntax element in multi-layer coding.

A fifth potential issue with using HEVC SEI messages in a multi-layercontext is that an active parameter sets SEI message is permitted to benested in HEVC. However, as noted above, the active parameter sets SEImessage is applicable to all layers. Accordingly, providing theflexibility of the active parameter sets SEI message to be applied toparticular layers of a multi-layer bitstream (e.g., using a nesting SEImessage) may needlessly increase the complexity of video encoder 20and/or video decoder 30. For example, upon receiving and decoding ascalable nesting SEI message, video decoder 30 may have to performadditional operations (e.g., versus non-nested SEI messages) todetermine the applicable layers for the scalable nesting SEI message.

According to a fifth aspect of this disclosure, an active parameter setsSEI message is disallowed to be nested in a scalable nesting SEImessage. For example, video encoder 20 and/or video decoder 30 may beconstrained to code an active parameter sets SEI message of amulti-layer bitstream only in a non-nested SEI message and not in ascalable nesting SEI message. The techniques may reduce thecomputational complexity associated with coding and using activeparameter sets SEI messages. For example, returning to the exampleabove, video decoder 30 may code and use the active parameter sets SEImessage without performing the additional operations associated withscalable nesting SEI messages.

A sixth potential issue with using HEVC SEI messages in a multi-layercontext is that the semantics of a nested SEI message having abitstream_subset_flag syntax element that is equal to one and apayloadType equal to 2, 3, 6, 9, 15, 16, 17, 19, 22, 23, 45, 47, 128,131, 132 or 134 (e.g., one of the SEI messages that have a payloadTypethat is not equal to any of 0, 1, 4, 5, 130, and 133) are not clear. InHEVC, the bitstream_subset_flag indicates whether the SEI messagescontained in the scalable nesting SEI message apply to specific layersor sub-layers of a multi-layer bitstream. For example, abitstream_subset_flag that is equal to zero specifies that the SEImessages contained in the scalable nesting SEI message apply to specificlayers or sub-layers. A bitstream_subset_flag that is equal to onespecifies that the SEI messages contained in the scalable nesting SEImessage apply to one or more sub-bitstreams resulting from asub-bitstream extraction process. Hence, HEVC does not clearly specifythe manner in which particular SEI messages (having the payload typesidentified above) are handled when a particular layer set (e.g., asub-bitstream) is extracted from a multi-layer bitstream, which maycreate errors and/or inefficiencies during multi-layer coding.

When payloadType is equal to 2, 3, 6, 9, 15, 16, 17, 19, 22, 23, 45, 47,128, 129, 131, 132 or 134, the SEI message is one of: a pan-scanrectangle SEI message that includes data associated with displaying at adifferent picture aspect ratio than a picture aspect ratio of outputpictures; a filler payload SEI message that includes data for adjustinga bit rate to meet specific constraints; a recovery point SEI messagethat includes information for clean random access or gradual decodingrefresh; a scene information SEI message that includes informationassociated with scene changes and transitions; a picture snapshot SEImessage that includes an indication to label an associated decodedpicture as a still-image snapshot of video content; a progressiverefinement segment start SEI message that includes informationassociated with a start of a segment of consecutive pictures thatrepresent a progressive refinement of quality of a picture rather than amoving scene; a progressive refinement segment end SEI message thatincludes information associated with an end of the segment ofconsecutive pictures; a film grain characteristics SEI message thatincludes information associated with synthesizing film grain effects; apost filter hint SEI message that includes information associated withsuggested post-filter coefficients or correlation information forpost-filter design; a tone mapping information SEI message that includesinformation associated with remapping to another color space than thatused or assumed in encoding; a frame packing arrangement SEI messagethat includes information associated with packing of stereoscopic videointo the bitstream; a display orientation SEI message that includesinformation that specifies flipping and/or rotation to be applied to theoutput pictures when the output pictures are displayed; a structure ofpictures information SEI message that includes information thatdescribes temporal and inter prediction structure of the bitstream; atemporal sub-layer zero index SEI message that indicates a temporalsub-layer zero index; a decoded picture has SEI message, or a regionrefresh information SEI message that indicates whether the slicesegments associated with the current SEI message belong to the refreshedregion in the current picture, respectively.

When payloadType is equal to 0, 1, 4, 5, 130, and 133, the SEI messageis one of: a buffering period SEI message, a picture timing SEI message,a user registered SEI message, a user unregistered SEI message, adecoding unit information SEI message, or a scalable nesting SEImessage, respectively.

According to a sixth aspect of this disclosure, when a scalable nestingSEI message contains an SEI message that has payloadType that is equalto 2, 3, 6, 9, 15, 16, 17, 19, 22, 23, 45, 47, 128, 131, 132, or 134(e.g., one of the SEI messages that have payloadType that is not equalto any of 0, 1, 4, 5, 130, and 133), the value of the syntax elementbitstream_subset_flag of the scalable nesting SEI message is required tobe equal to 0. For example, according to aspects of this disclosure,video encoder 20 and/or video decoder 30 may automatically determineand/or code the syntax element bitstream_subset_flag based on thepayload type of the SEI message being included in a predetermined set ofSEI messages. The predetermined set of SEI messages may be SEI messagesthat are applied to a single layer. In this manner, video encoder 20and/or video decoder 30 are constrained from applying the SEI messageincluded in the above-identified set from being applied to more than onelayer in a multi-layer bitstream, thereby potentially reducing errorsand/or inefficiencies during multi-layer coding.

A seventh potential issue with using HEVC SEI messages in a multi-layercontext is that it is unclear what the layer identifier value(nuh_layer_id) should be for an SEI NAL unit containing a non-nestedbuffering period, picture timing, or decoding unit information SEImessage. A buffering period SEI message provides an initial codedpicture buffer (CPB) removal delay and initial CPB removal delay offsetinformation for initialization of the HRD at the position of theassociated access unit in decoding order. The picture timing SEI messageprovides a picture output time and picture/sub-picture removal time forHRD operation, as well as picture structure related information. Adecoding unit information SEI message provides CPB removal delayinformation for a decoding unit. The message may be used invery-low-delay buffering operations. Accordingly, the above-noted SEImessages provide information that is needed by the HRD and the SEImessage are applicable to a layer set (e.g., a self-contained set oflayers also referred to as a sub-bitstream). If such SEI messages arenot nested and the layer identifier is not zero, it is unclear to whichlayer sets the messages apply, which may create errors duringmulti-layer coding.

According to a seventh aspect of this disclosure, the value of the layeridentifier (nuh_layer_id) for an SEI NAL unit containing a non-nestedbuffering period, picture timing, or decoding unit information SEImessage is required to be equal to 0. For example, according to aspectsof this disclosure, video encoder 20 and/or video decoder 30 mayautomatically determine that a layer identifier of the layer is zerovalued (and/or code a zero value for the layer identifier syntaxelement) based on the one or more non-VCL NAL units containing the SEImessage containing a non-nested buffering period SEI message, a picturetiming SEI message, or a decoding unit information SEI message. In thismanner, the techniques may potentially reduce errors and/orinefficiencies during multi-layer coding.

An eighth potential issue with using HEVC SEI messages in a multi-layercontext is that it is unclear what the value of a layer identifiersyntax element (nuh_layer_id) should be for a non-nested SEI messagehaving a payloadType equal to 2, 3, 6, 9, 15, 16, 17, 19, 22, 23, 45,47, 128, 131, 132, or 134 (i.e. one of the SEI messages that havepayloadType not equal to any of 0, 1, 129, 130, and 133). For example,HEVC does not clearly specify the manner in which particular SEImessages (having the payload types identified above) are handled forparticular layers (having a particular layer identifier) of amulti-layer bitstream, which may create errors and/or inefficienciesduring multi-layer coding.

According to an eighth aspect of this disclosure, when a non-nested SEImessage has payloadType equal to 2, 3, 6, 9, 15, 16, 17, 19, 22, 23, 45,47, 128, 131, 132, or 134 (i.e. one of the SEI messages that havepayloadType not equal to any of 0, 1, 129, 130, and 133), a value of alayer identifier (nuh_layer_id) for the SEI NAL unit containing thenon-nested SEI message is required to be equal to the layer identifier(nuh_layer_id) of the SEI NAL unit's associated VCL NAL units. That is,for example, video encoder 20 and/or video decoder 30 may automaticallydetermine, based on the SEI payload type being included in a first setof payload types (e.g., the payload types identified above), that alayer identifier syntax element for the non-VCL NAL units containing theSEI message is equal to a layer identifier syntax element of the VCL NALunits associated with the SEI message.

A ninth potential issue with using HEVC SEI messages in a multi-layercontext is that a prefix SEI message is required in HEVC to be presentand precede the first VCL NAL unit of an access unit in instances inwhich there is a prefix SEI message of the same type between two VCL NALunits of the access unit. For example, prefix SEI messages are typicallyincluded in a bitstream prior to the VCL NAL units to which the SEImessage applies. In HEVC, the restriction on the placement of prefix SEImessages is access unit based, which may present an issue for accessunits having multiple layer components (e.g., access units havingpictures from multiple layers). That is, some prefix SEI messages maynot be located in the appropriate location (e.g., prior to the VCL NALunits to which the SEI message applies) in access units having multiplelayer components.

According to a ninth aspect of this disclosure, video encoder 20 and/orvideo decoder 30 may control the manner in which prefix SEI messages arecoded based on the picture to which the prefix SEI messages apply (e.g.,in contrast to the above-noted access unit based techniques). Forexample, according to aspects of this disclosure, a prefix SEI messagethat applies to a layer (e.g., layerA) containing a picture is requiredto be present and precede the first VCL NAL unit of the picture ininstances in which there is a prefix SEI message that is of the sametype and applies to the layer (e.g., layerA) present between two VCL NALunits of the picture.

For example, for an access unit that includes at least a first pictureand a second picture, video encoder 20 and/or video decoder 30 may beconstrained to code one or more non-VCL NAL units containing a firstprefix SEI message applicable to VCL NAL units of the first picture, andone or more non-VCL NAL units containing a second prefix SEI messageapplicable to VCL NAL units of the second picture following the firstpicture in the bitstream. In this manner, video encoder 20 and/or videodecoder 30 are constrained from coding prefix SEI messages in otherlocations of an access unit, which may increase efficiency and reducestorage overhead for multi-layer coding.

A tenth potential issue with using HEVC SEI messages in a multi-layercontext is that, in HEVC, a suffix SEI message is required to be presentand succeed (follow) the fast VCL NAL unit of an access unit when thereis a suffix SEI message of the same type between two VCL NAL units ofthe access unit. For example, suffix SEI message is typically includedin a bitstream after the VCL NAL units to which the SEI message applies.In HEVC, the restriction on the placement of suffix SEI messages isaccess unit based, which may present an issue for access units havingmultiple layer components (e.g., access units of a multi-layerbitstream). That is, some suffix SEI messages may not be located in theappropriate location (e.g., following to the VCL NAL units to which theSEI message applies) in access units having multiple layer components.

According to a tenth aspect of this disclosure, video encoder 20 and/orvideo decoder 30 may control the manner in which suffix SEI messages arecoded based on the picture to which the suffix SEI messages apply (e.g.,in contrast to the above-noted access unit based techniques). Forexample, according to aspects of this disclosure, a suffix SEI messagethat applies to a layer (e.g., layerA) containing a picture is requiredto be present and succeed (follow) the last VCL NAL unit of the picturewhen there is a suffix SEI message that is of the same type and appliesto the layer (e.g., layerA) present between two VCL NAL units of thepicture.

For example, for an access unit that includes at least a first pictureand a second picture, video encoder 20 and/or video decoder 30 may beconstrained to code one or more non-VCL NAL units containing a firstsuffix SEI message applicable to VCL NAL units of the first picturefollowing the first picture, and one or more non-VCL NAL unitscontaining a second prefix SEI message applicable to VCL NAL units ofthe second picture following the second picture in the bitstream. Inthis manner, video encoder 20 and/or video decoder 30 are constrainedfrom coding suffix SEI messages in other locations of an access unit,which may increase efficiency and reduce storage overhead formulti-layer coding.

An eleventh potential issue with using HEVC SEI messages in amulti-layer context is that, in HEVC, the number of times an SEI messageis permitted to be repeated is specified per access unit. For example,in some instances, an SEI message may be repeated when coding a picture.In an example for purposes of illustration, for a picture having eightslices, each slice being associated with its own VCL NAL unit, videoencoder 20 and/or video decoder 30 may repeat a particular SEI messagefor each VCL NAL unit. However, an access unit-based restriction on thenumber of times an SEI message may be repeated may present an issue inmulti-layer video coding, because an access unit having multiple layercomponents may potentially have many more slices than an access unithaving a single layer component (e.g., a single picture). In thisexample, error performance (and/or other functions impacted by SEImessages) may be adversely affected.

According to an eleventh aspect of this disclosure, video encoder 20and/or video decoder 30 may specify the number of times an SEI messagemay be repeated on a per picture basis. In this context, a picture maybe defined as containing the VCL NAL units of a coded picture and thenon-VCL NAL units that are associated with the VCL NAL units. Hence,according to aspects of this disclosure, video encoder 20 and/or videodecoder 30 may determine a maximum repetition parameter for an SEImessage (e.g., a maximum number of times that the SEI message may berepeated) based on a picture unit that contains VCL NAL units of apicture and associated non-VCL NAL units of the picture. The techniquesmay, in some instances, increase error resilience in multi-layer coding.

A twelfth potential issue with using HEVC SEI messages in a multi-layercontext is that a conflict may arise in instances in which adefault_op_flag syntax element is equal to one, and abitstream_subset_flag syntax element is equal to one, but there are nolayer sets specified by a VPS for the bitstream that includes and onlyincludes the layers having layer identifier values (nuh_layer_id) in therange of 0 to nuh_layer_id of the current SEI NAL unit, inclusive. Forexample, a default_op_flag syntax element that is equal to one specifiesthat a maxTemporalId[0] is equal to nuh_temporal_id_plus1 of the currentSEI NAL unit minus 1 and that nestingLayerIdList[0] contains all integervalues in the range of 0 to nuh_layer_id of the current SEI NAL unit,inclusive, in increasing order of the values. As noted above, abitstream_subset_flag syntax element equal to one specifies that the SEImessages contained in the scalable nesting SEI message apply to one ormore sub-bitstreams resulting from a sub-bitstream extraction process.In other words, a conflict may arise in instances in which a defaultlayer set of a multi-layer bitstream is indicated, but the VPS does notspecify a particular layer set that corresponds to the default layerset.

According to a twelfth aspect of this disclosure, when abitstream_subset_flag syntax element is equal to one and none of thelayer sets specified by a VPS includes and only includes the layershaving nuh_layer_id values in the range of 0 to nuh_layer_id of thecurrent SEI NAL unit, inclusive, the value of the default_op_flag syntaxelement is required to be equal to zero. For example, video encoder 20and/or video decoder 30 may code a bitstream_subset_flag syntax elementof a multi-layer bitstream, and, based on the bitstream_subset_flagbeing equal to one and no layer sets specified by VPS of the multi-layerbitstream including layer identifiers in the range of zero to a layeridentifier of the non-VCL NAL units containing the SEI message,inclusive, determine that a value of a default_op_flag syntax element ofthe multi-layer bitstream is zero valued. The techniques may improveerror resilience when using the default_op_flag syntax element inmulti-layer coding.

A thirteenth potential issue with using HEVC SEI messages in amulti-layer context is that when a nesting_op_flag syntax element isequal to zero and an all_layers_flag syntax element is equal one, thevalue of the variable maxTemporalId[0] is unspecified in HEVC. Anesting_op_flag syntax element that is equal to zero specifies that thelist nestingLayerIdList[0] is specified by an all_layers_flag syntaxelement and, when present, nesting_layer_id[i] for all i values in therange of 0 to nesting_num_layers_minus 1, inclusive, and that thevariable maxTemporalId[0] is specified bynesting_no_op_max_temporal_id_plus1. In other words, HEVC does notspecify the applicable sub-layers (e.g., as identified using themaxTemporalId[0] variable) when nested SEI messages are used withtemporal sub-layers of a multi-layer bitstream, which may causeunnecessary complications.

According to a thirteenth aspect of this disclosure, when anesting_op_flag syntax element is equal to zero and an all_layers_flagsyntax element is equal one, video encoder 20 and video decoder 30 mayautomatically code a maxTemporalId[0] syntax element to have a value ofsix, which is the maximum possible value for the TemporalId syntaxelement. That is, according to aspects of this disclosure, video encoder20 and/or video decoder 30 may be configured to apply an SEI message toall sub-layers that are included in a layer of video data, regardless ofthe number of sub-layers that are included. In this manner, thetechniques may reduce the complexity associated with multi-layer coding.

A fourteenth potential issue with using HEVC SEI messages in amulti-layer context is that, when a nested SEI message has payloadTypeequal to 2, 3, 6, 9, 15, 16, 17, 19, 22, 23, 45, 47, 128, 131, 132, or134 (e.g., one of the SEI messages that have payloadType not equal toany of 0, 1, 4, 5, 130, and 133) and the SEI message applies to a set oflayers, the set of layers may be associated with a value ofmaxTemporalId[i] that is less than the greatest value of TemporalId inthe bitstream. However, the semantics of these SEI messages aredescribed without considering sub-layers, and are consequentlyinconsistent with the semantics of the scalable nesting SEI message whenthe above situation occurs. This inconsistency may needlessly increasethe complexity of multi-layer coding.

According to a fourteenth aspect of this disclosure, when a nested SEImessage has payloadType equal to 2, 3, 6, 9, 15, 16, 17, 19, 22, 23, 45,47, 128, 131, 132, or 134 (e.g., one of the SEI messages that havepayloadType not equal to any of 0, 1, 4, 5, 130, and 133), the SEI NALunit containing the scalable nesting SEI message is required to have aTemporalId syntax element that is equal to zero and a maxTemporalId[i]syntax element for all i to be equal to six, which is the maximumpossible value for the TemporalId syntax element. For example, videoencoder 20 and/or video decoder 30 may be configured to automaticallydetermine a value for the TemporalId syntax element that is equal tozero and a maxTemporalId[i] syntax element for all i that is equal tosix based on an SEI message having a payload type in a predetermined setof payload types (e.g., the types identified above). In this manner, thetechniques may reduce the complexity associated with multi-layer coding.

A fifteenth potential issue with using HEVC SEI messages in amulti-layer context is that when a bitstream_subset_flag syntax elementis equal to one and a nesting_op_flag syntax element is equal to zero,the HEVC standard permits a nestingLayeridList[0] syntax element tocorrespond to a layer set that is not specified by a VPS for themulti-layer bitstream.

According to a fifteenth aspect of this disclosure, when abitstream_subset_flag syntax element is equal to one and anesting_op_flag syntax element is equal to zero, video encoder 20 and/orvideo decoder 30 may be configured to code the nestingLayeridList[0]syntax element to include and only include the nuh_layer_id values ofone of the layer sets specified by the VPS. For example, video encoder20 and/or video decoder 30 may be configured to code abitstream_subset_flag syntax element of the multi-layer bitstream and anesting_op_flag syntax element of the multi-layer bitstream, and, basedon the bitstream_subset_flag syntax element having a value of one andthe nesting_op_flag syntax element having a value of zero, determinethat a nestingLayeridList[0] of the multi-layer bitstream includes onlylayer identifier values of a layer set specified in a VPS of themulti-layer bitstream. In this manner, the techniques may reduce thecomplexity associated with multi-layer coding.

The techniques described above may be applied independently or appliedin combination. Detailed examples that are consistent with thisdisclosure are set forth below. Text changes relative to the above-notedSHVC standard for some of the techniques described above are indicatedusing underlines to identify inserted material and double brackets([[removed:]]) to indicate deleted material below:

Change the following definitions in clause 3 as follows:

-   3.X access unit: A set of NAL units that are associated with each    other according to a specified classification rule, are consecutive    in decoding order, and contain the VCL NAL units of all coded    pictures associated with the same output time and their associated    non-VCL NAL units.    -   NOTE—Pictures in the same access unit are associated with the        same picture order count.        Add the following definitions to clause 3:-   3.X base bitstream partition: A bitstream partition that is also a    conforming bitstream itself.-   3.X bitstream partition: A sequence of bits, in the form of a NAL    unit stream or a byte stream, that is a subset of a bitstream    according to a partitioning.-   3.X output layer: A layer of an output layer set that is output when    TargetOptLayerSetIdx is equal to the index of the output layer set.-   3.X output layer set: A set of layers consisting of the layers of    one of the specified layer sets, where one or more layers in the set    of layers are indicated to be output layers.-   3.X output operation point: A bitstream that is created from another    bitstream by operation of the sub-bitstream extraction process with    the another bitstream, a target highest TemporalId, and a target    layer identifier list as inputs, and that is associated with a set    of target output layers.-   3.X picture unit: A set of NAL units that are associated with each    other according to a specified classification rule, are consecutive    in decoding order, and contain the VCL NAL units of a coded picture    and their associated non-VCL NAL units.-   3.X target output layer: A layer that is to be output and is one of    the output layers of the output layer set with index olsIdx such    that TargetOptLayerSetIdx is equal to olsIdx.-   3.X target output layer set: An output layer set associated with    variable TargetOptLayerSetIdx that specifies a layer identifier list    of an output operation point in use and a set of target output    layers.    C.1. General

This annex specifies the hypothetical reference decoder (HRD) and itsuse to check bitstream and decoder conformance.

Multiple tests may be needed for checking the conformance of abitstream, which is referred to as the bitstream under test. For eachtest, the following steps apply in the order listed:

-   -   1. An output operation point, under test, denoted as TargetOp,        is selected by selecting a target output layer set identified by        TargetOutputLayerSetIdx and selecting a target highest        TemporalId value HighestTid. The value of        TargetOutputLayerSetIdx shall be in the range of 0 to        NumOutputLayerSets−1, inclusive. The value of HighestTid shall        be in the range of 0 to vps_max_sub_layers_minus1, inclusive.        The variables TargetDecLayerSetIdx, TargetOptLayerIdList, and        TargetDecLayerIdList are then derived as specified by Equation        8-1. The output operation point under test has OptLayerIdList        equal to TargetOptLayerIdList, OpLayerIdList equal to        TargetDecLayerIdList, and OpTid equal to HighestTid.

For each output operation point under test when the bitstream-specificCPB operation is tested, the number of bitstream conformance tests to beperformed is equal to n0*n1*(n2*2+n3)*n4, where the values of n0, n1,n2, n3, and n4 are specified as follows:

Modify subclause D.3.1 as follows:

It is a requirement of bitstream conformance that when a prefix SEImessage with payloadType equal to 17 (progressive refinement segmentend) or 22 (post-filter hint) is present in an access unit, a suffix SEImessage with the same value of payloadType shall not be present in thesame access unit access unit.

It is a requirement of bitstream conformance that the followingrestrictions apply on containing of SEI messages in SEI NAL units:

-   -   An SEI NAL unit containing an active parameter sets SEI message        shall contain only one active parameter sets SEI message and        shall not contain any other SEI messages.    -   When an SEI NAL unit contains a non-nested buffering period SEI        message, a non-nested picture timing SEI message, or a        non-nested decoding unit information SEI message, the SEI NAL        unit shall not contain any other SEI message with payloadType        not equal to 0 (buffering period), 1 (picture timing), or 130        (decoding unit information).    -   When an SEI NAL unit contains a nested buffering period SEI        message, a nested picture timing SEI message, or a nested        decoding unit information SEI message, the SEI NAL unit shall        not contain any other SEI message with payloadType not equal to        0 (buffering period), 1 (picture timing), 130 (decoding unit        information), or 133 (scalable nesting).

Let prevVclNalUnitInAu of an SEI NAL unit or an SEI message be thepreceding VCL NAL unit in decoding order, if any, in the same accessunit, and nextVclNalUnitInAu of an SEI NAL unit or an SEI message be thenext VCL NAL unit in decoding order, if any, in the same access unit. Itis a requirement of bitstream conformance that the followingrestrictions apply;

It is a requirement of bitstream conformance that the followingrestrictions apply on order of SEI messages:

-   -   When an SEI NAL unit containing an active parameter sets SEI        message is present in an access unit, it shall be the first SEI        NAL unit that follows the prevVclNalUnitInAu of the SEI NAL unit        and precedes the next VclNalUnitInAu of the SEI NAL unit.    -   When a non-nested buffering period SEI message is present in an        access unit, it shall not follow any other SEI message that        follows the prevVclNalUnitInAu of the buffering period SEI        message and precedes the nextVclNalUnitInAu of the buffering        period SEI message, other than an active parameter sets SEI        message.    -   When a non-nested picture timing SEI message is present in an        access unit, it shall not follow any other SEI message that        follows the prevVclNalUnitInAu of the picture timing SEI message        and precedes the nextVclNalUnitInAu of the picture timing SEI        message, other than an active parameter sets SEI message or a        non-nested buffering period SEI message.    -   When a non-nested decoding unit information SEI message is        present in an access unit, it shall not follow any other SEI        message in the same access unit that follows the        prevVclNalUnitInAu of the decoding unit information SEI message        and precedes the nextVclNalUnitInAu of the decoding unit        information SEI message, other than an active parameter sets SEI        message, a non-nested buffering period SEI message, or a        non-nested picture timing SEI message.    -   When a nested buffering period SEI message, a nested picture        timing SEI message, or a nested decoding unit information SEI        message is contained in a scalable nesting SEI message in an        access unit, the scalable nesting SEI message shall not follow        any other SEI message that follows the prevVclNalUnitInAu of the        scalable nesting SEI message and precedes the nextVclNalUnitInAu        of the scalable nesting SEI message, other than an active        parameter sets SEI message, a non-nested buffering period SEI        message, a non-nested picture timing SEI message, a non-nested        decoding unit information SEI message, or another scalable        nesting SEI message that contains a buffering period SEI        message, a picture timing SEI message, or a decoding unit        information SEI message.    -   When payloadType is equal to 0 (buffering period), 1 (picture        timing), or 130 (decoding unit information) for an SEI message,        nested or non-nested, within the access unit, the SEI NAL unit        containing the SEI message shall precede all NAL units of any        picture unit that has nuh_layer_id greater than        highestAppLayerId, where highestAppLayerId is the greatest value        of nuh_layer_id of ail the layers in all the operation points        that the SEI message applies to.    -   When payloadType is equal to 2, 3, 6, 9, 15, 16, 17, 19, 22, 23,        45, 47, 128, 131, 132, or 134 (i.e. one of the SEI messages that        have payloadType not equal to any of 0, 1, 4, 5, 130, and 133)        for an SEI message, nested or non-nested, within the access        unit, the SEI NAL unit containing the SEI message shall precede        all NAL units of any picture unit that has nuh_layer_id greater        than highestAppLayerId, where highestAppLayerId is the greatest        value of nuh_layer_id of all the layers that the SEI message        applies.

The following applies on the applicable operation points or layers ofSEI messages:

-   -   For a non-nested SEI message, when payloadType is equal to 0        (buffering period), 1 (picture timing), or 130 (decoding unit        information), the non-nested SEI message applies to the        operation point that has OpTid equal to the greatest value of        nuh_temporal_id_plus1 among all VCL NAL units in the bitstream,        and that has OpLayerIdList containing all values of nuh_layer_id        in all VCL units in the bitstream.    -   For a non-nested SEI message, when payloadType is equal to 2, 3,        6, 9, 15, 16, 17, 19, 22, 23, 45, 47, 128, 131, 132, or 134        (i.e. one of the SEI messages that have payloadType not equal to        any of 0, 1, 4, 5, 130, and 133), the non-nested SEI message        applies to the layer for which the VCL NAL units have        nuh_layer_id equal to the nuh_layer_id of the SEI NAL unit        containing the SEI message.    -   An active parameter sets SEI message, which cannot be nested,        applies to all layers in the bitstream.    -   When frame_field_info_present_flag is equal to 1 for a picture        timing information SEI message, nested or non-nested, the frame        field information carried in the syntax elements pic_struct        source_scan_type, and duplicate_flag applies to all the layers        in all the operation points that the picture timing SEI message        applies to.

It is a requirement of bitstream conformance that the followingrestrictions apply on nesting of SEI messages:

-   -   An SEI message that has payloadType equal to 129 (active        parameter sets), 132 (decoded picture hash), and 133 scalable        nesting shall not be nested in a scalable nesting SEI message.    -   When a scalable nesting SEI message contains a buffering period        SEI message, a picture timing SEI message, or a decoding unit        information SEI message, the scalable nesting SEI message shall        not contain any other SEI message with payloadType not equal to        0 (buffering period), 1 (picture timing), or 130 (decoding unit        information).    -   When a scalable nesting SEI message contains a buffering period        SEI message, a picture timing SEI message, or a decoding unit        information SEI message, the value of bitstream_subset_flag of        the scalable nesting SEI message shall be equal to 1.    -   When a scalable nesting SEI message contains an SEI message that        has payloadType equal to 2, 3, 6, 9, 15, 16, 17, 19, 22, 23, 45,        47, 128, 131, 132, or 134 (i.e. one of the SEI messages that        have payloadType not equal to any of 0, 1, 4, 5, 130, and 133),        the value of bitstream_subset_flag of the scalable nesting SEI        message shall be equal to 0.

It is a requirement of bitstream conformance that the followingrestrictions apply on the values of nuh_layer_id and TemporalId of SEINAL units:

-   -   When a non-nested SEI message has payloadType equal to 2, 3, 6,        9, 15, 16, 17, 19, 22, 23, 45, 47, 128, 131, 132, or 134 (i.e.        one of the SEI messages that have payloadType not equal to any        of 0, 1, 4, 5, 129, 130, and 133), the SEI NAL unit containing        the non-nested SEI message shall have TemporalId equal to the        TemporalId of the access unit containing the SEI NAL unit.    -   When a non-nested SEI message has payloadType equal to 0, 1,        129, or 130, the SEI NAL unit containing the non-nested SEI        message shall have nuh_layer_id equal to 0.    -   When a non-nested SEI message has payloadType equal to 2, 3, 6,        9, 15, 16, 17, 19, 22, 23, 45, 47, 128, 131, 132, or 134 (i.e.        one of the SEI messages that have payloadType not equal to any        of 0, 1, 129, 130, and 133), the SEI NAL unit containing the        non-nested SEI message shall have null_layer_id equal to the        nuh_layer_id of the SEI NAL unit's associated VCL NAL unit.

NOTE 4—For an SEI NAL unit containing a scalable nesting SEI message,the values of TemporalId and nuh_layer_id should be set equal to thelowest value of TemporalId and nuh_layer_id, respectively, of all thesub-layers or operation points the nested SEI messages apply to.

It is a requirement of bitstream conformance that the followingrestrictions apply on the presence of SEI messages between two VCL NALunits of picture:

-   -   When there is a prefix SEI message that has payloadType equal to        0, 1, 2, 3, 6, 9, 15, 16, 17, 19, 22, 23, 45, 47, 128, 129, or        131 (i.e. one of the prefix SEI messages that are not user data        registered by Rec. ITU-T T.35 SEI message, user data        unregistered SEI message, decoding unit information SEI message,        scalable nesting SEI message, or region refresh information SEI        message) and applies to a picture of a layer layerA present        between two VCL NAL units of the picture in decoding order,        there shall be a prefix SEI message that is of the same type and        applies to the layer layerA present in the same access unit        preceding the first VCL NAL unit of the picture.    -   When there is a suffix SEI message that has payloadType equal to        3 (filler payload), 17 (progressive refinement segment end), 22        (post filter hint), or 132 (decoded picture hash) and applies to        a picture of a layer layerA present between two VCL NAL units of        picture.

It is a requirement of bitstream conformance that the followingrestrictions apply on repetition of SEI messages:

-   -   For each of the following payloadType values, there shall be        less than or equal to 8 identical sei_payload( ) syntax        structures within a picture unit: 0, 1, 2, 6, 9, 15, 16, 17, 19,        2.2, 23, 45, 47, 128, 129, 131, 132, and 133.    -   There shall be less than or equal to 8 identical sei_payload( )        syntax structures with payloadType equal to 130 within a        decoding unit.    -   The number of identical sei_payload( ) syntax structures with        payloadType equal to 134 in a picture unit shall be less than or        equal to the number of slice segments in the picture unit.

Modify subclause D.3.23 as follows:

The scalable nesting SEI message provides a mechanism to associate SEImessages with bitstream subsets corresponding to various operationpoints or with specific layers or sub-layers.

A scalable nesting SEI message contains one or more SEI messages.

bitstream_subset_flag equal to 0 specifies that the SEI messagescontained in the scalable nesting SEI message apply to specific layersor sub-layers. bitstream_subset_flag equal to 1 specifies that the SEImessages contained in the scalable nesting SEI message apply to one ormore sub-bitstreams resulting from a sub-bitstream extraction process asspecified in clause 10 with inputs based on the syntax elements of thescalable nesting SEI message as specified below.

Depending on the value of bitstream_subset_flag, the layers orsub-layers, or the operation points to which the SEI messages containedin the scalable nesting SEI message apply are specified by deriving thelists nestingLayedIdList[i] and the variables maxTemporalId[i] based onsyntax element values as specified below.

nesting_op_flag equal to 0 specifies that the list nestingLayerIdList[0]is specified by all_layers_flag and, when present, nesting_layer_id[i]for all i values in the range of 0 to nesting_num_layers_minus1,inclusive, and that the variable maxTemporalId[0] is specified bynesting_no_op_max_temporal_id_plus1, nesting_op_flag equal to 1specifies that the list nestingLayerIdList[i] and the variablemaxTemporalId[i] are specified by nesting_num_ops_minus1,default_op_flag, nesting_max_temporal_id_plus1[i], when present, andnesting_op_idx[i], when present.

default_op_flag equal to 1 specifies that maxTemporalId[0] is equal tonull_temporal_id_plus1 of the current SEI NAL unit minus 1 and thatnestingLayerIdList[0] contains all integer values in the range of 0 tonuh_layer_id of the current SEI NAL unit, inclusive, in increasing orderof the values.

When bitstream_subset_flag is equal to 1 and none of the layer setsspecified by the VPS includes and only includes the layers havingnuh_layer_id values in the range of 0 to nuh_layer_id of the current SEINAL unit inclusive, the value of default_op_flag shall be equal to 0.

nesting_num_ops_minus1 plus 1 minus default_op_flag specifies the numberof the following nesting_op_idx[i] syntax elements. The value ofnesting_num_ops_minus1 shall be in the range of 0 to 1023, inclusive.

If nesting_op_flag is equal to 0, the variable nestingNumOps is setequal to 1. Otherwise, the variable nestingNumOps is set equal tonesting_num_ops_minus1+1.

nesting_max_temporal_id_plus1[i] is used to specify the variablemaxTemporalId[i]. The value of nesting_max_temporal_id_plus1[i] shall begreater than or equal to nuh_temporal_id_plus1 of the current SEI NALunit. The variable maxTemporalId[i] is set equal tonesting_max_temporal_id_plus1[i]−1.

nesting_op_idx[i] is used to specify the list nestingLayerIdList[i]. Thevalue of nesting_op_idx[i] shall be in the range of 0 to 1023,inclusive.

The list nestingLayerIdList[i] is set equal to the OpLayerIdList of thenesting_op_idx[i]-th layer set specified by the active VPS.

all_layers_flag equal to 0 specifies that the list nestingLayerIdList[0]is specified by nesting_layer_id[i] for all i values in the range of 0to nesting_num_layers_minus1, inclusive, all_layers_flag equal to 1specifies that the list nestingLayerIdList[0] consists of all values ofnuh_layer_id present in the current access unit that are greater than orequal to nuh_layer_id of the current SEI NAL unit, in increasing orderof the values.

Note: When nuh_layer_id of the SEI NAL unit containing the scalablenesting SEI message is greater than 0, bitstream_subset_flag andall_layers_flag cannot both be equal to 1, because in this case theapplicable operation point of the nested SEI messages would not includethe base layer and consequently the sub-bitstream corresponding to theapplicable operation point would be a non-conforming bitstream.

When nesting_op_flag is equal to 0 and all_layers_flag is equal 1,maxTemporalId[0] is set equal to 6.

nesting_no_op_max_temporal_id_plus1 minus 1 specifies the value ofmaxTemporalId[0] when nesting_op_flag is equal to 0 and all_layers_flagis equal to 0. The value of nesting_no_op_max_temporal_id_plus1 shallnot be equal to 0.

nesting_num_layers_minus1 plus 1 specifies the number of the followingnesting_layer_id[i] syntax elements. The value ofnesting_num_layers_minus1 shall be in the range of 0 to 63, inclusive.

nesting_layer_id[i] specifies the i-th nuh_layer_id value included inthe list nestingLayerIdList[0].

For any i and j in the range of 0 to nesting_num_layers_minus1,inclusive, with i less than j, nesting_layer_id[i] shall be less thannesting_layer_id[j].

The list nestingLayerIdList[0] is set to consist of nesting_layer_id[i]for all i values in the range of 0 to nesting_num_layers_minus1,inclusive, in increasing order of i values.

When bitstream_subset_flag is equal to 0, the following applies:

-   -   The SEI messages contained in the scalable nesting SEI message        apply to the sets of layers or sub-layers subLayerSet[i] for all        i values in the range of 0 to nestingNumOps−1, inclusive, where        the VCL NAL units of the layers or sub-layers in each set        subLayerSet[i] have nuh_layer_id values that are included in the        list nestingLayerIdList[i] and TemporalId values that are in the        range of the TemporalId of the current SEI NAL unit to        maxTemporalId[i], inclusive.    -   When a nested SEI message has payloadType equal to 2, 3, 6, 9,        15, 16, 17, 19, 22, 23, 45, 47, 128, 131, 132, or 134 (i.e. one        of the SEI messages that have payloadType not equal to any of 0,        1, 4, 5, 130, and 133), the nuh_layer_id of the SEI NAL unit        containing the scalable nesting SEI message shall have        TemporalId equal to 0 and maxTemporalId[i] for all i shall be        equal to 6.    -   When a nested SEI message has payloadType equal to 2, 3, 6, 9,        15, 16, 17, 19, 22, 23, 45, 47, 128, 131, 132, or 134 (i.e. one        of the SEI messages that have payloadType not equal to any of 0,        1, 4, 5, 130, and 133) and the value of nestingNumOps is greater        than 0, the nested SEI message applies to all layers for which        each nuh_layer_id is included in at least one of the lists        nestingLayerIdList[i] with i ranging from 0 to nestingNumOps−1,        inclusive.

When bitstream_subset_flag is equal to 1, the SEI messages contained inthe scalable nesting SEI message apply to the operation pointscorresponding to the sub-bitstreams subBitstream[i] for all i values inthe range of 0 to nestingNumOps−1, inclusive, where each sub-bitstreamsubBitstream[i] is the output of the sub-bitstream extraction process ofclause 10 with the bitstream, maxTemporalId[i], andnestingLayerIdList[i] as inputs.

When bitstream_subset_flag is equal to 1 and nesting_op_flag is equal to0, nestingLayeridList[0] shall include and only include the nuh_layer_idvalues of one of the layer sets specified by the VPS.

nesting_zero_bit shall be equal to 0.

F.3 Definitions

For the purpose of this annex, the following definitions apply inaddition to the definitions in clause 3. These definitions are eithernot present in clause 3 or replace definitions in clause 3.

F.3.1 alternative output layer: A layer that is a direct reference layeror an indirect reference layer of an output layer and which may includea picture that may be output when no picture of the output layer ispresent in the access unit containing the picture.

F.7.4.3.1 Video Parameter Set RBSP Semantics

The specifications in subclause 7.4.3.1 apply with followingmodifications and additions:

-   -   layerSetLayerIdList is replaced by LayerSetLayerIdList.    -   numLayersInIdList is replaced by NumLayersInIdList.    -   Replace “Each operation point is identified by the associated        layer identifier list, denoted as OpLayerIdList, which consists        of the list of nuh_layer_id values of all NAL units included in        the operation point, in increasing order of nuh_layer_id values,        and a variable OpTid, which is equal to the highest TemporalId        of all NAL units included in the operation point.” with “Each        operation point is identified by the associated layer identifier        list, denoted as OpLayerIdList which consists of the list of        nuh_layer_id values of all NAL units included in the operation        point, in increasing order of nuh_layer_id values, and a        variable OpTid, which is equal to the highest TemporalId of all        NAL units included in the operation point. Each output operation        point is associated with an operation point and identified by        the a list of nuh_layer_id values of all the pictures that are        to be output, in increasing order of nuh_layer_id values,        denoted as OptLayerIdList, and the OpTid of the associated        operation point. The OpLayerIdList of the operation point        associated with an output operation point is also referred to as        the OpLayerIdList of the output operation point

FIG. 2 is a block diagram illustrating an example video encoder 20 thatmay implement the techniques described in this disclosure. FIG. 2 isprovided for purposes of explanation and should not be consideredlimiting of the techniques as broadly exemplified and described in thisdisclosure. For purposes of explanation, this disclosure describes videoencoder 20 in the context of HEVC coding. However, the techniques ofthis disclosure may be applicable to other coding standards or methods.

Video encoder 20 may be configured to output video to post-processingentity 27, which is another example device that may implement thetechniques described in this disclosure. Post-processing entity 27 isintended to represent an example of a video entity, such as a mediaaware network element (MANE), a splicing/editing device or anotherintermediate device that may process encoded video data from videoencoder 20. In some instances, post-processing entity 27 may be anexample of a network entity. In some video encoding systems,post-processing entity 27 and video encoder 20 may be parts of separatedevices, while in other instances, the functionality described withrespect to post-processing entity 27 may be performed by the same devicethat comprises video encoder 20.

Video encoder 20 may perform intra- and inter-coding of video blockswithin video slices. Infra-coding relies on spatial prediction to reduceor remove spatial redundancy in video within a given video frame orpicture. Inter-coding relies on temporal prediction to reduce or removetemporal redundancy in video within adjacent frames or pictures of avideo sequence. Intra-mode (I mode) may refer to any of several spatialbased compression modes. Inter-modes, such as uni-directional prediction(P mode) or bi-prediction (B mode), may refer to any of severaltemporal-based compression modes.

In the example of FIG. 2, video encoder 20 includes a partitioning unit35, prediction processing unit 41, filter unit 63, reference picturememory 64, summer 50, transform processing unit 52, quantization unit54, and entropy encoding unit 56. Prediction processing unit 41 includesmotion estimation unit 42, motion compensation unit 44, andinfra-prediction processing unit 46. For video block reconstruction,video encoder 20 also includes inverse quantization unit 58, inversetransform processing unit 60, and summer 62. Filter unit 63 is intendedto represent one or more loop filters such as a deblocking filter, anadaptive loop filter (ALF), and a sample adaptive offset (SAO) filter.Although filter unit 63 is shown in FIG. 2 as being an in loop filter,in other configurations, filter unit 63 may be implemented as a postloop filter.

As shown in FIG. 2, video encoder 20 receives video data, andpartitioning unit 35 partitions the data into video blocks. Thispartitioning may also include partitioning into slices, tiles, or otherlarger units, as wells as video block partitioning, e.g., according to aquadtree structure of LCUs and CUs. Video encoder 20 generallyillustrates the components that encode video blocks within a video sliceto be encoded. The slice may be divided into multiple video blocks (andpossibly into sets of video blocks referred to as tiles). Predictionprocessing unit 41 may select one of a plurality of possible codingmodes, such as one of a plurality of intra coding modes or one of aplurality of inter coding modes, for the current video block based onerror results (e.g., coding rate and the level of distortion).Prediction processing unit 41 may provide the resulting intra- orinter-coded block to summer 50 to generate residual block data and tosummer 62 to reconstruct the encoded block for use as a referencepicture.

Intra-prediction processing unit 46 within prediction processing unit 41may perform infra-predictive coding of the current video block relativeto one or more neighboring blocks in the same frame or slice as thecurrent block to be coded to provide spatial compression. Motionestimation unit 42 and motion compensation unit 44 within predictionprocessing unit 41 perform inter-predictive coding of the current videoblock relative to one or more predictive blocks in one or more referencepictures to provide temporal compression.

Motion estimation unit 42 may be configured to determine theinter-prediction mode for a video slice according to a predeterminedpattern for a video sequence. The predetermined pattern may designatevideo slices in the sequence as P slices or B slices. Motion estimationunit 42 and motion compensation unit 44 may be highly integrated, butare illustrated separately for conceptual purposes. Motion estimation,performed by motion estimation unit 42, is the process of generatingmotion vectors, which estimate motion for video blocks. A motion vector,for example, may indicate the displacement of a PU of a video blockwithin a current video frame or picture relative to a predictive blockwithin a reference picture.

A predictive block is a block that is found to closely match the PU ofthe video block to be coded in terms of pixel difference, which may bedetermined by sum of absolute difference (SAD), sum of square difference(SSD), or other difference metrics. In some examples, video encoder 20may calculate values for sub-integer pixel positions of referencepictures stored in reference picture memory 64. For example, videoencoder 20 may interpolate values of one-quarter pixel positions,one-eighth pixel positions, or other fractional pixel positions of thereference picture. Therefore, motion estimation unit 42 may perform amotion search relative to the full pixel positions and fractional pixelpositions and output a motion vector with fractional pixel precision.

Motion estimation unit 42 calculates a motion vector for a PU of a videoblock in an inter-coded slice by comparing the position of the PU to theposition of a predictive block of a reference picture. The referencepicture may be selected from a first reference picture list (List 0) ora second reference picture list (List 1), each of which identify one ormore reference pictures stored in reference picture memory 64. Motionestimation unit 42 sends the calculated motion vector to entropyencoding unit 56 and motion compensation unit 44.

Motion compensation, performed by motion compensation unit 44, mayinvolve fetching or generating the predictive block based on the motionvector determined by motion estimation, possibly performinginterpolations to sub-pixel precision. Upon receiving the motion vectorfor the PU of the current video block, motion compensation unit 44 maylocate the predictive block to which the motion vector points in one ofthe reference picture lists. Video encoder 20 forms a residual videoblock by subtracting pixel values of the predictive block from the pixelvalues of the current video block being coded, forming pixel differencevalues. The pixel difference values form residual data for the block,and may include both luma and chroma difference components. Summer 50represents the component or components that perform this subtractionoperation. Motion compensation unit 44 may also generate syntax elementsassociated with the video blocks and the video slice for use by videodecoder 30 in decoding the video blocks of the video slice.

Intra-prediction processing unit 46 may intra-predict a current block,as an alternative to the inter-prediction performed by motion estimationunit 42 and motion compensation unit 44, as described above. Inparticular, intra-prediction processing unit 46 may determine anintra-prediction mode to use to encode a current block. In someexamples, intra-prediction processing unit 46 may encode a current blockusing various intra-prediction modes, e.g., during separate encodingpasses, and intra-prediction processing unit 46 (or mode select unit 40,in some examples) may select an appropriate intra-prediction mode to usefrom the tested modes. For example, intra-prediction processing unit 46may calculate rate-distortion values using a rate-distortion analysisfor the various tested intra-prediction modes, and select theintra-prediction mode having the best rate-distortion characteristicsamong the tested modes. Rate-distortion analysis generally determines anamount of distortion (or error) between an encoded block and anoriginal, unencoded block that was encoded to produce the encoded block,as well as a bit rate (that is, a number of bits) used to produce theencoded block. Intra-prediction processing unit 46 may calculate ratiosfrom the distortions and rates for the various encoded blocks todetermine which intra-prediction mode exhibits the best rate-distortionvalue for the block.

In any case, after selecting an intra-prediction mode for a block,infra-prediction processing unit 46 may provide information indicativeof the selected intra-prediction mode for the block to entropy encodingunit 56. Entropy encoding unit 56 may encode the information indicatingthe selected intra-prediction mode in accordance with the techniques ofthis disclosure. Video encoder 20 may include in the transmittedbitstream configuration data, which may include a plurality ofintra-prediction mode index tables and a plurality of modifiedintra-prediction mode index tables (also referred to as codeword mappingtables), definitions of encoding contexts for various blocks, andindications of a most probable intra-prediction mode, anintra-prediction mode index table, and a modified intra-prediction modeindex table to use for each of the contexts.

After prediction processing unit 41 generates the predictive block forthe current video block via either inter-prediction or intra-prediction,video encoder 20 forms a residual video block by subtracting thepredictive block from the current video block. The residual video datain the residual block may be included in one or more TUs and applied totransform processing unit 52. Transform processing unit 52 transformsthe residual video data into residual transform coefficients using atransform, such as a discrete cosine transform (DCT) or a conceptuallysimilar transform. Transform processing unit 52 may convert the residualvideo data from a pixel domain to a transform domain, such as afrequency domain.

Transform processing unit 52 may send the resulting transformcoefficients to quantization unit 54. Quantization unit 54 quantizes thetransform coefficients to further reduce bit rate. The quantizationprocess may reduce the bit depth associated with some or all of thecoefficients. The degree of quantization may be modified by adjusting aquantization parameter. In some examples, quantization unit 54 may thenperform a scan of the matrix including the quantized transformcoefficients. Alternatively, entropy encoding unit 56 may perform thescan.

Following quantization, entropy encoding unit 56 entropy encodes thequantized transform coefficients. For example, entropy encoding unit 56may perform context adaptive variable length coding (CAVLC), contextadaptive binary arithmetic coding (CABAC), syntax-based context-adaptivebinary arithmetic coding (SBAC), probability interval partitioningentropy (PIPE) coding or another entropy encoding methodology ortechnique. Following the entropy encoding by entropy encoding unit 56,the encoded bitstream may be transmitted to video decoder 30, orarchived for later transmission or retrieval by video decoder 30.Entropy encoding unit 56 may also entropy encode the motion vectors andthe other syntax elements for the current video slice being coded.

Inverse quantization unit 58 and inverse transform processing unit 60apply inverse quantization and inverse transformation, respectively, toreconstruct the residual block in the pixel domain for later use as areference block of a reference picture. Motion compensation unit 44 maycalculate a reference block by adding the residual block to a predictiveblock of one of the reference pictures within one of the referencepicture lists. Motion compensation unit 44 may also apply one or moreinterpolation filters to the reconstructed residual block to calculatesub-integer pixel values for use in motion estimation. Summer 62 addsthe reconstructed residual block to the motion compensated predictionblock produced by motion compensation unit 44 to produce a referenceblock for storage in reference picture memory 64. The reference blockmay be used by motion estimation unit 42 and motion compensation unit 44as a reference block to inter-predict a block in a subsequent videoframe or picture.

According to aspects of this disclosure, video encoder 20 may beconfigured to generate a number of syntax elements, such as the syntaxelements associated with SEI messages described above, including SEImessages for multi-layer codecs. For example, video encoder 20 may beconfigured to generate syntax elements according to any combination ofthe fifteen aspects described above with respect to FIG. 1. In someinstances, video encoder 20 may encode such syntax elements usingentropy encoding unit 56 or another unit responsible for encoding dataand generating an encoded bitstream. Furthermore, post-processing entity27 of FIG. 2 is another example device that may implement the techniquesdescribed in this disclosure with respect to SEI messages, including SEImessages for multi-layer codecs.

FIG. 3 is a block diagram illustrating an example video decoder 30 thatmay implement the techniques described in this disclosure. FIG. 3 isprovided for purposes of explanation and is not limiting on thetechniques as broadly exemplified and described in this disclosure. Forpurposes of explanation, this disclosure describes video decoder 30 inthe context of HEVC coding. However, the techniques of this disclosuremay be applicable to other coding standards or methods.

In the example of FIG. 3, video decoder 30 includes an entropy decodingunit 80, prediction processing unit 81, inverse quantization unit 86,inverse transform processing unit 88, summer 90, filter unit 91, andreference picture memory 92. Prediction processing unit 81 includesmotion compensation unit 82 and intra-prediction processing unit 84.Video decoder 30 may, in some examples, perform a decoding passgenerally reciprocal to the encoding pass described with respect tovideo encoder 20 from FIG. 2.

During the decoding process, video decoder 30 receives an encoded videobitstream that represents video blocks of an encoded video slice andassociated syntax elements from video encoder 20. Video decoder 30 mayreceive the encoded video bitstream from network entity 78. Networkentity 78 may, for example, be a server, a MANE, a video editor/splicer,or other such device configured to implement one or more of thetechniques described above. Network entity 78 may or may not include avideo encoder, such as video encoder 20. Some of the techniquesdescribed in this disclosure may be implemented by network entity 78prior to network entity 78 transmitting the encoded video bitstream tovideo decoder 30. In some video decoding systems, network entity 78 andvideo decoder 30 may be parts of separate devices, while in otherinstances, the functionality described with respect to network entity 78may be performed by the same device that comprises video decoder 30.

Entropy decoding unit 80 of video decoder 30 entropy decodes thebitstream to generate quantized coefficients, motion vectors, and othersyntax elements. Entropy decoding unit 80 forwards the motion vectorsand other syntax elements to prediction processing unit 81. Videodecoder 30 may receive the syntax elements at the video slice leveland/or the video block level.

When the video slice is coded as an intra-coded (I) slice,intra-prediction processing unit 84 of prediction processing unit 81 maygenerate prediction data for a video block of the current video slicebased on a signaled intra-prediction mode and data from previouslydecoded blocks of the current frame or picture. When the video frame iscoded as an inter-coded (i.e., B or P) slice, motion compensation unit82 of prediction processing unit 81 produces predictive blocks for avideo block of the current video slice based on the motion vectors andother syntax elements received from entropy decoding unit 80. Thepredictive blocks may be produced from one of the reference pictureswithin one of the reference picture lists. Video decoder 30 mayconstruct the reference frame lists, List 0 and List 1, using defaultconstruction techniques based on reference pictures stored in referencepicture memory 92.

Motion compensation unit 82 determines prediction information for avideo block of the current video slice by parsing the motion vectors andother syntax elements, and uses the prediction information to producethe predictive blocks for the current video block being decoded. Forexample, motion compensation unit 82 uses some of the received syntaxelements to determine a prediction mode (e.g., infra- orinter-prediction) used to code the video blocks of the video slice, aninter-prediction slice type (e.g., B slice or P slice), constructioninformation for one or more of the reference picture lists for theslice, motion vectors for each inter-encoded video block of the slice,inter-prediction status for each inter-coded video block of the slice,and other information to decode the video blocks in the current videoslice.

Motion compensation unit 82 may also perform interpolation based oninterpolation filters. Motion compensation unit 82 may use interpolationfilters as used by video encoder 20 during encoding of the video blocksto calculate interpolated values for sub-integer pixels of referenceblocks. In this case, motion compensation unit 82 may determine theinterpolation filters used by video encoder 20 from the received syntaxelements and use the interpolation filters to produce predictive blocks.

Inverse quantization unit 86 inverse quantizes, i.e., de-quantizes, thequantized transform coefficients provided in the bitstream and decodedby entropy decoding unit 80. The inverse quantization process mayinclude use of a quantization parameter calculated by video encoder 20for each video block in the video slice to determine a degree ofquantization and, likewise, a degree of inverse quantization that shouldbe applied. Inverse transform processing unit 88 applies an inversetransform, e.g., an inverse DCT, an inverse integer transform, or aconceptually similar inverse transform process, to the transformcoefficients in order to produce residual blocks in the pixel domain.

After motion compensation unit 82 generates the predictive block for thecurrent video block based on the motion vectors and other syntaxelements, video decoder 30 forms a decoded video block by summing theresidual blocks from inverse transform processing unit 88 with thecorresponding predictive blocks generated by motion compensation unit82. Summer 90 represents the component or components that perform thissummation operation. If desired, loop filters (either in the coding loopor after the coding loop) may also be used to smooth pixel transitions,or otherwise improve the video quality.

Filter unit 91 is intended to represent one or more loop filters such asa deblocking filter, an adaptive loop filter (ALF), and a sampleadaptive offset (SAO) filter. Although filter unit 91 is shown in FIG. 3as being an in loop filter, in other configurations, filter unit 91 maybe implemented as a post loop filter. The decoded video blocks in agiven frame or picture are then stored in reference picture memory 92,which stores reference pictures used for subsequent motion compensation.Reference picture memory 92 also stores decoded video for laterpresentation on a display device, such as display device 31 of FIG. 1.

According to aspects of this disclosure, video decoder 30 may beconfigured to parse and decode a number of syntax elements, such as thesyntax elements associated with SEI messages described above, includingSEI messages for multi-layer codecs. For example, video decoder 30 maybe configured to parse and decode syntax elements according to anycombination of the fifteen aspects described above with respect toFIG. 1. In some instances, video decoder 30 may decode such syntaxelements using entropy decoding unit 80 or another unit responsible fordecoding data from an encoded bitstream. Furthermore, network entity 78of FIG. 3 (which may be a media aware network element) is anotherexample device that may implement the techniques described in thisdisclosure with respect to SEI messages, including SEI messages formulti-layer codecs.

FIG. 4 is a block diagram illustrating encapsulation unit 21 in moredetail. In the example of FIG. 4, encapsulation unit 21 includes a videoinput interface 100, an audio input interface 102, a video file creationunit 104, and a video file output interface 106. Video file creationunit 104, in this example, includes a supplemental enhancementinformation (SEI) message generation unit 108, a view identifier (ID)assignment unit 110, a representation creation unit 112, and anoperation point creation unit 114.

Video input interface 100 and audio input interface 102 receive encodedvideo and audio data, respectively. While not shown in the example ofFIG. 1, source device 12 may also include an audio source and audioencoder to generate audio data and encode audio data, respectively.Encapsulation unit 21 may then encapsulate the encoded audio data andthe encoded video data to form a video file. Video input interface 100and audio input interface 102 may receive encoded video and audio dataas the data is encoded, or may retrieve encoded video and audio datafrom a computer-readable medium. Upon receiving encoded video and audiodata, video input interface 100 and audio input interface 102 pass theencoded video and audio data to video file creation unit 104 forassembly into a video file.

Video file creation unit 104 may correspond to a control unit includinghardware, software, and/or firmware configured to perform the functionsand procedures attributed thereto. The control unit may further performthe functions attributed to encapsulation unit 21 generally. Forexamples in which video file creation unit 104 is embodied in softwareand/or firmware, encapsulation unit 21 may include a computer-readablemedium comprising instructions for video file creation unit 104 and aprocessing unit to execute the instructions. Each of the sub-units ofvideo file creation unit 104 (SEI message generation unit 108, view IDassignment unit 110, representation creation unit 112, and operationpoint creation unit 114, in this example) may be implemented asindividual hardware units and/or software modules, and may befunctionally integrated or further separated into additional sub-units.

Video file creation unit 104 may correspond to any suitable processingunit or processing circuitry, such as, for example, one or moremicroprocessors, application-specific integrated circuits (ASICs), fieldprogrammable gate arrays (FPGAs), digital signal processors (DSPs), orany combination thereof. Video file creation unit 104 may furtherinclude a non-transitory computer-readable medium storing instructionsfor any or all of SEI message generation unit 108, view ID assignmentunit 110, representation creation unit 112, and operation point creationunit 114, as well as a processor for executing the instructions.

In general, video file creation unit 104 may create one or more videofifes including the received audio and video data. Video file creationunit 104 may construct a media presentation description (MPD) formultimedia content including two or more views. In other examples, videofile creation unit 104 may create a manifest storing data similar tothat of the MPD for the multimedia content.

SEI message generation unit 108 may represent a unit that generates SEImessages. SEI message generation unit 108 may, in accordance with thetechniques described in this disclosure, be configured to generate anumber of syntax elements, such as the syntax elements associated withSEI messages described above, including SEI messages for multi-layercodecs. For example, SEI message generation unit 108 may be configuredto generate syntax elements according to any combination of the fifteenaspects described above with respect to FIG. 1.

View ID assignment unit 110 may assign view identifiers to each of theviews of the multimedia content. Representation creation unit 112 mayconstruct one or more representations for the multimedia content, eachof which may include one or more of the views for the multimediacontent. In some examples, view ID assignment unit 110 may include datain the MPD and/or the representations (e.g., header data for therepresentations) indicating a maximum and a minimum of the viewidentifiers for views included in the representations. In addition,representation creation unit 112 may provide information in the MPD thatindicates whether larger view IDs correspond to views having cameraperspectives to the right or to the left of camera perspectives forviews having smaller view IDs.

In some examples, the same layer may be encoded using various encodingcharacteristics, such as different frame rates, different bit rates,different encoding schemes, or other differences. Representationcreation unit 112 may ensure that each layer included in a commonrepresentation is encoded according to the same encodingcharacteristics. In this manner, the MPD and/or header data for therepresentation may signal a set of characteristics (or attributes) forthe representation that applies to all layers in the representation.Moreover, representation creation unit 112 may create multiplerepresentations including the same layers, albeit with potentiallydifferent encoding characteristics. In some examples, representationcreation unit 112 may encapsulate each layer of multimedia content inindividual representations. In such examples, to output more than onelayer, destination device 14 may request two or more representations ofthe multimedia content.

Operation point creation unit 114 may create operation points for one ormore representations of the multimedia content. In general, an operationpoint corresponds to a subset of views in a representation that aretargeted for output, where each of the views shares a common temporallevel. As one example an operation point may be identified by atemporal_id value representing the target temporal level and a set ofview_id values representing the target output views. One operation pointmay be associated with a bitstream subset, which consists of the targetoutput views and all other views on which the target output viewsdepend.

Video file output interface 106 may output the created video file. Forexample, video file output interface 106 may be configured to providethe created video file to output interface 22, as described above withrespect to FIG. 1.

While the techniques of FIG. 4 are described with encapsulation unit 21for purposes of example, it should be understood that similar techniquesmay be performed by other video processing units, such as decapsulationunit 29 (FIG. 1), video encoder 20, or video decoder 30. For example,decapsulation unit 29 may be configured to receive a multi-layerbitstream and parse/decode the above-noted syntax from the multi-layerbitstream.

FIG. 5 is a block diagram illustrating an example set of devices thatform part of network 120. In this example, network 120 includes routingdevices 124A, 124B (routing devices 124) and transcoding device 126.Routing devices 124 and transcoding device 126 are intended to representa small number of devices that may form part of network 120. Othernetwork devices, such as switches, hubs, gateways, firewalls, bridges,and other such devices may also be included within network 120.Moreover, additional network devices may be provided along a networkpath between server device 122 and client device 128. Server device 122may correspond to source device 12 (FIG. 1), while client device 128 maycorrespond to destination device 14 (FIG. 1), in some examples.

In general, routing devices 124 implement one or more routing protocolsto exchange network data through network 120. In some examples, routingdevices 124 may be configured to perform proxy or cache operations.Therefore, in some examples, routing devices 124 may be referred to asproxy devices. In general, routing devices 124 execute routing protocolsto discover routes through network 120. By executing such routingprotocols, routing device 124B may discover a network route from itselfto server device 122 via routing device 124A. One or more of routingdevices 124 may comprise a MANE that uses one or more aspects of thisdisclosure.

The techniques of this disclosure may be implemented by network devicessuch as routing devices 124 and transcoding device 126, but also may beimplemented by client device 128. In this manner, routing devices 124,transcoding device 126, and client device 128 represent examples ofdevices configured to perform the techniques of this disclosure.Moreover, the devices of FIG. 1, and encoder 20 illustrated in FIG. 2and decoder 30 illustrated in FIG. 3, are also exemplary devices thatcan be configured to perform the techniques of this disclosure.

FIG. 6 is a flow diagram illustrating an example operation of a videoprocessing device configured to code an SEI message in accordance withvarious aspects of the techniques described in this disclosure. In theexample of FIG. 6, a video processing device, such as video encoder 20,encapsulation unit 21, decapsulation unit 29, post-processing entity 27,network entity 78, obtains one or more VCL NAL units of a first layer ofa multi-layer bitstream (140). For example, in instances in which thevideo processing device is a video encoder or a video decoder, the videoprocessing device may encode the VCL NAL units in a multi-layerbitstream or decode the VCL NAL units from a multi-layer bitstream. Inexamples in which the video processing device is not configured toencode or decode such VCL NAL units, the video processing device mayparse and obtain the VCL NAL units from a multi-layer bitstream.

The video processing device also codes (e.g., encodes or decodes) an SEImessage that is applicable to the VCL NAL units of the first layer to betogether with the first layer in the multi-layer bitstream (142). Forexample, according to aspects of this disclosure, the video processingdevice only codes the non-VCL NAL units containing the SEI messageapplicable to the VCL NAL units of the first layer together with the VCLNAL units of the first layer, and does not include the SEI message withother layers of the multi-layer bitstream. For example, according toaspects of this disclosure, the multi-layer bitstream does not containany coded pictures of any other layer of the multi-layer bitstreambetween the VCL NAL units of the first layer and the non-VCL NAL unitscontaining the SEI message applicable to the VCL NAL units of the firstlayer. In this manner, the SEI message remains together with the layerto which the SEI message applies for access units having multiple layercomponents. In some examples, the video processing device may code theSEI message to be directly adjacent to the VCL NAL units to which themessage applies in the multi-layer bitstream.

In some examples, the VCL NAL units of the first layer are VCL NAL unitsof a first picture of the first layer and the SEI message is a prefixSEI message applicable to the first picture of the first layer. In suchexamples, only coding the non-VCL NAL units containing the prefix SEImessage together with the VCL NAL units may include only coding thenon-VCL NAL units preceding the VCL NAL units in the bitstream. That is,the video processing device may code the non-VCL NAL units containingthe SEI message to be located immediately prior to the VCL NAL units ofthe first picture in the multi-layer bitstream.

In some examples, the VCL NAL units of the first layer are VCL NAL unitsof a first picture of the first layer and the SEI message is a suffixSEI message applicable to the first picture of the first layer. In suchexamples, only coding the non-VCL NAL units containing the suffix SEImessage together with the VCL NAL units may include only coding thenon-VCL NAL units subsequent to the VCL NAL units in the bitstream. Thatis, the video processing device may code the non-VCL NAL unitscontaining the SEI message to be located immediately following the VCLNAL units of the first picture in the multi-layer bitstream.

In the example of FIG. 6, the video processing device also obtains VCLNAL units of a second layer of the multi-layer bitstream (144). Forexample, the video processing device may code (i.e., encode or decode)slices of a picture of a second layer of the multi-layer bitstream. Thevideo processing device also codes an SEI message that is applicable tothe VCL NAL units of the second layer to be together with the VCL NALunits of the second layer (146). For example, as described above, thevideo processing device may code the multi-layer bitstream such that thebitstream does not contain any coded pictures of any other layer of themulti-layer bitstream between the VCL NAL units of the second layer andthe non-VCL NAL units containing the SEI message applicable to the VCLNAL units of the second layer. In this manner, the SEI message remainstogether with the layer to which the SEI message applies for accessunits having multiple layer components.

Again, in some examples, the video processing device may code one ormore non-VCL NAL units containing a second prefix SEI message applicableto VCL NAL units of the second picture following the first picture inthe bitstream. The video processing device may also code one or morenon-VCL NAL units containing a second suffix SEI message applicable toVCL NAL units of the second picture following the second picture in thebitstream.

In some instances, the video processing device may also determine amaximum repetition parameter for the SEI message based on a picture unitthat contains VCL NAL units of a first picture of the first layer andassociated non-VCL NAL units of the first picture.

It should also be understood that the steps shown and described withrespect to FIG. 6 are provided as merely one example. That is, the stepsshown in the example of FIG. 6 need not necessarily be performed in theorder shown in FIG. 6, and fewer, additional, or alternative steps maybe performed. Moreover, while the techniques are generically describedabove with respect to a video processing device, the techniques may beimplemented by a variety of video processing devices, such as videoencoder 20, encapsulation unit 21, decapsulation unit 29,post-processing entity 27, network entity 78, or other processing units.

FIG. 7 is a flow diagram illustrating another example operation of avideo processing device configured to code an SEI message in accordancewith various aspects of the techniques described in this disclosure. Inthe example of FIG. 7, a video processing device, such as video encoder20, encapsulation unit 21, decapsulation unit 29, post-processing entity27, network entity 78, codes one or more non-VCL NAL units of a layer ofa multi-layer bitstream that contain a decoded picture hash SEI message(150). As noted above, a decoded picture hash message may provide achecksum derived from the sample values of a decoded picture. Thedecoded picture hash message may be used, e.g., by a video decoder suchas video decoder 30, for detecting whether a picture was correctlyreceived and decoded.

The video processing device also determines a layer identifierassociated with the non-VCL NAL units (152). The video processing devicealso determines a set of layers of the multi-layer bitstream to whichthe decoded picture hash SEI message is applicable based on a layeridentifier of the non-VCL NAL units containing the decoded picture hashSEI message (154). According to aspects of this disclosure, the set ofapplicable layers of a decoded picture hash SEI message may be specifiedto be the layer with the layer identifier (nuh_layer_id) that is equalto the layer identifier (nuh_layer_id) of the SEI NAL unit containingthe SEI message. That is, the decoded picture hash SEI message onlyapplies to the layer that has the same layer identifier (nuh_layer_id)of the SEI NAL unit that contains the SEI message. In some instances,the decoded picture hash SEI message may only be a non-nested SEImessage.

In some examples, additionally or alternatively, the video processingdevice may also code one or more second non-VCL NAL units of themulti-layer bitstream. The second non-VCL NAL units may contain anactive parameter sets SEI message that indicates the parameter sets thatare active for a particular portion of video data. The video processingdevice may also determine that the active parameter sets SEI message isapplicable to all layers of the multi-layer bitstream based on the oneor more second non-VCL NAL units containing the active parameter set SEImessage. That is, the video processing device may determine that theactive parameter sets SEI message is applicable to all layers of themulti-layer bitstream by virtue of the SEI message being an activeparameter sets SEI message. In some examples, the video processingdevice may further code one or more syntax elements indicating that theactive parameter sets SEI message is applicable to all layers of themulti-layer bitstream. In some examples, the video processing device mayonly code the active parameter sets SEI message as a non-nested SEImessage.

In some examples, additionally or alternatively, the video processingdevice may code one or more syntax elements indicating that frame fieldinformation is present in a picture timing SEI message of themulti-layer bitstream. The video processing device may also apply theframe field information to ail layers in all operation points of themulti-layer bitstream to which the picture timing SEI message applies.

It should also be understood that the steps shown and described withrespect to FIG. 7 are provided as merely one example. That is, the stepsshown in the example of FIG. 7 need not necessarily be performed in theorder shown in FIG. 7, and fewer, additional, or alternative steps maybe performed. Moreover, while the techniques are generically describedabove with respect to a video processing device, the techniques may beimplemented by a variety of video processing devices, such as videoencoder 20, encapsulation unit 21, decapsulation unit 29,post-processing entity 27, network entity 78, or other processing units.

FIG. 8 is a flow diagram illustrating another example operation of avideo processing device configured to code an SEI message in accordancewith various aspects of the techniques described in this disclosure. Inthe example of FIG. 8, a video processing device, such as video encoder20, encapsulation unit 21, decapsulation unit 29, post-processing entity27, network entity 78, may code one or more non-VCL NAL units of a layerof a multi-layer bitstream that contain an SEI message having an SEIpayload type (160). The video processing device may also determinessyntax of the multi-layer bitstream to which the SEI message appliesbased on the payload type (162). For example, the video processingdevice may determine one or more syntax values of the multi-layerbitstream to which the SEI message applies based on the SEI payloadtype.

For example, according to aspects of this disclosure, the SEI messagemay include a scalable nesting SEI message. In this example, the videoprocessing device may determine, based on the SEI payload type beingincluded in a first set of payload types, that a bitstream_subset_flagsyntax element of the scalable nesting SEI message is zero valued. In anexample, the first set of payload types includes payload types 2, 3, 6,9, 15, 16, 17, 19, 22, 23, 45, 47, 128, 131, 132, and 134, as describedabove with respect to FIG. 1, although the set may include more or fewerthan those identified in the example.

In another example, the SEI message may be a non-nested SEI message. Inthis example, the video processing device may determine, based on theSEI payload type being included in a first set of payload types, that alayer identifier syntax element for the non-VCL NAL units containing theSEI message is equal to a layer identifier syntax element of VCL NALunits associated with the SEI message. In an example, the first set ofpayload types includes payload types 2, 3, 6, 9, 15, 16, 17, 19, 22, 23,45, 47, 128, 131, 132, and 134, although the set may include more orfewer than those identified.

In still another example, the SEI message may be a scalable nesting SEImessage. In this example, the video processing device may determine,based on the SEI payload type being included in a first set of payloadtypes, that the one or more non-VCL NAL units containing the scalablenesting SEI message has a TemporalId that is equal to zero andmaxTemporalId[i] that is equal to seven for all values of i. In anexample, the first set of payload types includes payload types 2, 3, 6,9, 15, 16, 17, 19, 22, 23, 45, 47, 128, 131, 132, and 134, although theset may include more or fewer than those identified in the example.

According to aspects of this disclosure, additionally or alternatively,the video processing device may code an active parameter sets SEImessage of the multi-layer bitstream only in a non-nested SEI messageand not in a scalable nesting SEI message.

Additionally or alternatively, the video processing device may determinethat the layer identifier of the layer of multi-layer video data is zerovalued based on the SEI message containing a non-nested buffering periodSEI message, a picture timing SEI message, or a decoding unitinformation SEI message. In some examples, the video processing devicemay also code a layer identifier syntax element to have a zero value.

Additionally or alternatively, the video processing device may code abitstream_subset_flag syntax element of the multi-layer bitstream. Thevideo coding device may, based on the bitstream_subset_flag syntaxelement being equal to one and no layer sets specified by a videoparameter set (VPS) of the multi-layer bitstream including layeridentifiers in the range of zero to a layer identifier of the non-VCLNAL units containing the SEI message, inclusive, determine that a valueof a default_op_flag syntax element of the multi-layer bitstream is zerovalued. In some examples, the video processing device may also code thedefault_op_flag syntax element to have a zero value.

According to an additional aspect of this disclosure, additionally oralternatively, the video processing device may code a nesting_op_flag ofthe multi-layer bitstream and an all_layers_flag of the multi-layerbitstream. The video processing device may, based on the nesting_op_flaghaving a value of zero and the all_layers_flag having a value of one,determine that a value of a maxTemporalId[0] syntax element of themulti-layer bitstream is equal to seven. In some examples, the videoprocessing device may also code the maxTemporalId[0] syntax element tohave a value of seven.

Additionally or alternatively, the video processing device may code abitstream_subset_flag syntax element of the multi-layer bitstream and anesting_op_flag syntax element of the multi-layer bitstream. The videoprocessing device may, based on the bitstream_subset_flag syntax elementhaving a value of one and the nesting_op_flag syntax element having avalue of zero, determine that a nestingLayeridList[0] of the multi-layerbitstream includes only layer identifier values of a layer set specifiedin a VPS of the multi-layer bitstream. In some examples, the videoprocessing device may also code the a nestingLayeridList[0] syntaxelement to only include layer identifier values of a layer set specifiedin a VPS of the multi-layer bitstream.

It should also be understood that the steps shown and described with,respect to FIG. 8 are provided as merely one example. That is, the stepsshown in the example of FIG. 8 need not necessarily be performed in theorder shown in FIG. 8, and fewer, additional, or alternative steps maybe performed. Moreover, while the techniques are generically describedabove with respect to a video processing device, the techniques may beimplemented by a variety of video processing devices, such as videoencoder 20, encapsulation unit 21, decapsulation unit 29,post-processing entity 27, network entity 78, or other processing units.

In one or more examples, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over, as oneor more instructions or code, a computer-readable medium and executed bya hardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or earner wave. Data storage mediamay be any available media that can be accessed by one or more computersor one or more processors to retrieve instructions, code and/or datastructures for implementation of the techniques described in thisdisclosure. A computer program product may include a computer-readablemedium.

By way of example, and not limitation, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if instructions are transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transient media, but areinstead directed to non-transient, tangible storage media. Disk anddisc, as used herein, includes compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablelogic arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the term “processor,” as used herein may referto any of the foregoing structure or any other structure suitable forimplementation of the techniques described herein. In addition, in someaspects, the functionality described herein may be provided withindedicated hardware and/or software modules configured for encoding anddecoding, or incorporated in a combined codec. Also, the techniquescould be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A method of coding video data, the methodcomprising: coding one or more non-video coding layer (VCL) networkabstraction layer (NAL) units of a layer of a multi-layer bitstream,wherein the one or more non-VCL NAL units contain a non-nested decodedpicture hash SEI message; coding one or more syntax elements thatindicate a layer identifier of the one or more non-VCL NAL units; anddetermining a set of layers of the multi-layer bitstream to which thenon-nested decoded picture hash SEI message is applicable based on theone or more syntax elements that indicate the layer identifier of theone or more non-VCL NAL units containing the non-nested decoded picturehash SEI message.
 2. The method of claim 1, further comprising: coding apicture of the layer included in the set of layers; and checking thepicture for errors using the non-nested decoded picture hash SEImessage.
 3. The method of claim 1, further comprising: coding one ormore second non-VCL NAL units of the multi-layer bitstream, wherein theone or more second non-VCL NAL units contain an active parameter setsSEI message; and determining that the active parameter sets SEI messageis applicable to all layers of the multi-layer bitstream based on theone or more second non-VCL NAL units containing the active parameter setSEI message.
 4. The method of claim 3, wherein coding the one or moresecond non-VCL NAL units containing the active parameter sets SEImessage comprises only coding a non-nested SEI message.
 5. The method ofclaim 1, further comprising: coding one or more syntax elementsindicating that frame field information is present in a picture timingSEI message of the multi-layer bitstream; and applying the frame fieldinformation to all layers in all operation points to which the picturetiming SEI message applies.
 6. The method of claim 1, furthercomprising: coding the determined set layers of the multi-layerbitstream; using the non-nested decoded picture hash message todetermine whether the determined set of layers include one or moreerrors.
 7. The method of claim 6, wherein coding comprises encoding, andwherein encoding the determined set of layers comprises: generatingresidual data for the determined set of layers indicating a differencebetween predictive data and actual video data; applying a transform tothe residual data the generate transform coefficients; and generating abitstream that includes an indication of the transform coefficients. 8.The method of claim 1, wherein coding comprises decoding, and whereindecoding the determined set of layers comprises: obtaining transformcoefficients for the determined set of layers from an encoded bitstream;applying an inverse transform to the transform coefficients to generateresidual data; and determining the video data based on the generatedresidual data.
 9. A device for coding video data, the device comprising:a memory configured to store at least a portion of a multi-layerbitstream; and one or more processors configured to: code one or morenon-video coding layer (VCL) network abstraction layer (NAL) units of alayer of a multi-layer bitstream, wherein the one or more non-VCL NALunits contain a non-nested decoded picture hash SEI message; code one ormore syntax elements that indicate a layer identifier of the one or morenon-VCL NAL units; and determine a set of layers of the multi-layerbitstream to which the non-nested decoded picture hash SEI message isapplicable based on the one or more syntax elements that indicate thelayer identifier of the one or more non-VCL NAL units containing thenon-nested decoded picture hash SEI message.
 10. The device of claim 9,wherein the one or more processors are further configured to: code apicture of the layer included in the set of layers; and check thepicture for errors using the non-nested decoded picture hash SEImessage.
 11. The device of claim 9, wherein the one or more processorsare further configured to: code one or more second non-VCL NAL units ofthe multi-layer bitstream, wherein the one or more second non-VCL NALunits contain an active parameter sets SEI message; and determine thatthe active parameter sets SEI message is applicable to all layers of themulti-layer bitstream based on the one or more second non-VCL NAL unitscontaining the active parameter set SEI message.
 12. The device of claim11, wherein to code the one or more second non-VCL NAL units containingthe active parameter sets SEI message, the one or more processors areconfigured to only code a non-nested SEI message.
 13. The device ofclaim 9, wherein the one or more processors are further configured to:code one or more syntax elements indicating that frame field informationis present in a picture timing SEI message of the multi-layer bitstream;and apply the frame field information to all layers in all operationpoints to which the picture timing SEI message applies.
 14. The deviceof claim 9, wherein the one or more processors are further configuredto: code the determined set layers of the multi-layer bitstream; use thenon-nested decoded picture hash message to determine whether thedetermined set of layers include one or more errors.
 15. The device ofclaim 14, wherein coding comprises encoding, and wherein to encode thedetermined set of layers, the one or more processors are configured to:generate residual data for the determined set of layers indicating adifference between predictive data and actual video data; apply atransform to the residual data the generate transform coefficients; andgenerate a bitstream that includes an indication of the transformcoefficients.
 16. The device of claim 9, wherein coding comprisesdecoding, and wherein to decode the determined set of layers, the one ormore processors are configured to: obtain transform coefficients for thedetermined set of layers from an encoded bitstream; apply an inversetransform to the transform coefficients to generate residual data; anddetermine the video data based on the generated residual data.
 17. Thedevice of claim 9, wherein the device comprises at least one of: anintegrated circuit; a microprocessor; or a wireless communicationdevice.
 18. An apparatus for coding video data, the apparatuscomprising: means for coding one or more non-video coding layer (VCL)network abstraction layer (NAL) units of a layer of a multi-layerbitstream, wherein the one or more non-VCL NAL units contain anon-nested decoded picture hash SEI message; means for coding one ormore syntax elements that indicate a layer identifier of the one or morenon-VCL NAL units; and means for determining a set of layers of themulti-layer bitstream to which the non-nested decoded picture hash SEImessage is applicable based on the one or more syntax elements thatindicate the layer identifier of the one or more non-VCL NAL unitscontaining the non-nested decoded picture hash SEI message.
 19. Theapparatus of claim 18, further comprising: means for coding the pictureof a layer included in the set of layers; and means for checking thepicture for errors using the non-nested decoded picture hash SEImessage.
 20. A non-transitory computer-readable medium havinginstructions stored thereon that, when executed, cause one or moreprocessors to: code one or more non-video coding layer (VCL) networkabstraction layer (NAL) units of a layer of a multi-layer bitstream,wherein the one or more non-VCL NAL units contain a non-nested decodedpicture hash SEI message; code one or more syntax elements that indicatea layer identifier of the one or more non-VCL NAL units; and determine aset of layers of the multi-layer bitstream to which the non-nesteddecoded picture hash SEI message is applicable based on the one or moresyntax elements that indicate the layer identifier of the one or morenon-VCL NAL units containing the non-nested decoded picture hash SEImessage.
 21. The non-transitory computer-readable medium of claim 20,wherein the instructions further cause the one or more processors to:code a picture of the layer included in the set of layers; and check thepicture for errors using the non-nested decoded picture hash SEImessage.